Files missing on new 5TB hard drive after formatting as ext4 with parted and mkfs

Question

After connecting a new external 5TB hard drive and formatting it as ext4 with parted and mkfs with the procedure below, I then mounted the drive, copied files onto it, unmounted the drive and restarted its host computer (running Ubuntu 18.04.3 LTS). Upon mounting the drive again, the files were no longer on the drive. What am I doing wrong?

1. Got drive information using lshw:

   # sudo lshw -C disk
   *-disk
      description: ATA Disk
      product: ST2000LM015-2E81
      vendor: Seagate
      physical id: 0.0.0
      bus info: scsi@2:0.0.0
      logical name: /dev/sda
      version: SDM1
      serial: ZDZ5H230
      size: 1863GiB (2TB)
      capabilities: gpt-1.00 partitioned partitioned:gpt
      configuration: ansiversion=5 guid=2f8a9ef2-85cf-49fe-8cf6- 
      04d7caae1a08 logicalsectorsize=512 sectorsize=4096
   *-disk
      description: SCSI Disk
      product: Portable
      vendor: Seagate
      physical id: 0.0.0
      bus info: scsi@3:0.0.0
      logical name: /dev/sdb
      version: 9300
      serial: NAA5C9V7
      size: 4657GiB (5TB)
      capabilities: gpt-1.00 partitioned partitioned:gpt
      configuration: ansiversion=6 guid=bea19262-56ed-43c1-a4cd- 
      62bca45eeb62 logicalsectorsize=512 sectorsize=4096
   

2. Implemented ext4 file system using parted:

   # sudo parted /dev/sdb
   
   GNU Parted 3.2
   Using /dev/sdb
   Welcome to GNU Parted! Type 'help' to view a list of commands.
   (parted) mklabel gpt
   Warning: The existing disk label on /dev/sdb will be destroyed and all data on this disk will be lost. Do you want to continue?
   Yes/No? Yes
   (parted) unit TB
   (parted) mkpart
   Partition name?  []? 5tb
   File system type?  [ext2]? ext4
   Start? 0
   End? 5
   (parted) print
   Model: Seagate Portable (scsi)
   Disk /dev/sdb: 5.00TB
   Sector size (logical/physical): 512B/4096B
   Partition Table: gpt
   Disk Flags:
   Number  Start   End     Size    File system  Name  Flags
    1      0.00TB  5.00TB  5.00TB  ext4         5tb
   
   (parted) quit
   Information: You may need to update /etc/fstab.
   

3. Make or Build a Linux File System (use mkfs)

   # sudo mkfs -t ext4 /dev/sdb1
   mke2fs 1.44.1 (24-Mar-2018)
   /dev/sdb1 alignment is offset by 512 bytes.
   This may result in very poor performance, (re)-partitioning suggested.
   Creating filesystem with 1220933433 4k blocks and 152616960 inodes
   Filesystem UUID: e29ea500-1588-4128-9e12-b2f62891b318
   Superblock backups stored on blocks:
       32768, 98304, 163840, 229376, 294912, 819200, 884736, 1605632, 2654208,
       4096000, 7962624, 11239424, 20480000, 23887872, 71663616, 78675968,
       102400000, 214990848, 512000000, 550731776, 644972544
   
   Allocating group tables: done
   Writing inode tables: done
   Creating journal (262144 blocks): done
   Writing superblocks and filesystem accounting information: done
   

4. Manually mounted/unmount the Hard Drive using mount:

   Create a mount point:
   # sudo mkdir /media/5tb
   Manually mount the drive (not automatic at boot)
   # sudo mount /dev/sdb1 /media/5tb
   Unmount the drive
   # sudo umount /media/5tb
   

EXTENDED Sep 11, 2019:

Upon reboot, it appears the drives are "reversed" (ie the 5TB drive is now /dev/sda and the 2TB drive is now /dev/sdb):

root@nuc3:/media/5tb# sudo lshw -C disk
  *-disk
       description: SCSI Disk
       product: Portable
       vendor: Seagate
       physical id: 0.0.0
       bus info: scsi@0:0.0.0
       logical name: /dev/sda
       version: 9300
       serial: NAA5C9V7
       size: 4657GiB (5TB)
       capabilities: gpt-1.00 partitioned partitioned:gpt
       configuration: ansiversion=6 guid=657182bf-8953-4001-b0d0-4b81832b17e6 logicalsectorsize=512 sectorsize=4096
  *-disk
       description: ATA Disk
       product: ST2000LM015-2E81
       vendor: Seagate
       physical id: 0.0.0
       bus info: scsi@3:0.0.0
       logical name: /dev/sdb
       version: SDM1
       serial: ZDZ5H230
       size: 1863GiB (2TB)
       capabilities: gpt-1.00 partitioned partitioned:gpt
       configuration: ansiversion=5 guid=2f8a9ef2-85cf-49fe-8cf6-04d7caae1a08 logicalsectorsize=512 sectorsize=4096

@jos, I applied the fdisk to both drives:

# sudo fdisk -l /dev/sda
Disk /dev/sda: 4.6 TiB, 5000981077504 bytes, 9767541167 sectors
Units: sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 4096 bytes
I/O size (minimum/optimal): 4096 bytes / 4096 bytes
Disklabel type: gpt
Disk identifier: 657182BF-8953-4001-B0D0-4B81832B17E6

Device     Start        End    Sectors  Size Type
/dev/sda1  65535 9767533004 9767467470  4.6T Linux filesystem

Partition 1 does not start on physical sector boundary.

# sudo fdisk -l /dev/sdb
Disk /dev/sdb: 1.8 TiB, 2000398934016 bytes, 3907029168 sectors
Units: sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 4096 bytes
I/O size (minimum/optimal): 4096 bytes / 4096 bytes
Disklabel type: gpt
Disk identifier: 2F8A9EF2-85CF-49FE-8CF6-04D7CAAE1A08

Device       Start        End    Sectors  Size Type
/dev/sdb1     2048    1050623    1048576  512M EFI System
/dev/sdb2  1050624 3907026943 3905976320  1.8T Linux filesystem