hard drive - Re-Partitioning to Save My Data

I put about 1.5Tb of data on a 6T HDD, EXT4 format external USB drive, to bring halfway around the world. After I arrived, Ubuntu 18.04 does not "see" the drive when it is plugged into my laptop. The drive is not dead and communicates, but no access to data. I'm getting conflicting information from Ubuntu disk operation commands (below). Some say 1.6TB. Some say 5.5TB. HELP! How do I go about fixing this?

Refer to the last six or so lines in this post. There is a partitioning tool for windows, Aoemei Partition Assistant, which sees both partitions, but I don't know what to do to FIX the issue. I'm sure I only get one shot at fixing this and being able to use the data while I am here for another five months. It's all backed up, but it's 5000 miles away. Thanks in advance for assistance. I'm currently on GMT.

gparted says "The backup GPT table is corrupt, but the primary appears OK, so that will be used." It then says the entire drive is one partition that is 1.46 Tb UNALLOCATED.

sudo fdisk -l /dev/sdc
Disk /dev/sdc: 1.5 TiB, 1603128614912 bytes, 3131110576 sectors
Units: sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disklabel type: dos
Disk identifier: 0x00000000
Device     Boot Start        End    Sectors Size Id Type
/dev/sdc1           1 4294967295 4294967295   2T ee GPT
Command (m for help): v

Total allocated sectors 4294967296 greater than the maximum 3131110576.
Command (m for help): F
Unpartitioned space /dev/sdc: 0 B, 0 bytes, 0 sectors
Units: sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes

sudo gdisk /dev/sdc
GPT fdisk (gdisk) version 1.0.3
Warning! Disk size is smaller than the main header indicates! Loading
secondary header from the last sector of the disk! You should use 'v' to

verify disk integrity, and perhaps options on the experts' menu to repair
the disk.
Caution: invalid backup GPT header, but valid main header; regenerating
backup header from main header.
Warning! One or more CRCs don't match. You should repair the disk!
Partition table scan:
  MBR: protective
  BSD: not present
  APM: not present
  GPT: damaged

************************************************************************
Caution: Found protective or hybrid MBR and corrupt GPT. Using GPT, but disk verification and recovery are STRONGLY recommended.
************************************************************************
Command (? for help): p
Disk /dev/sdc: 3131110576 sectors, 1.5 TiB
Model: FANTOM DRIVE    
Sector size (logical/physical): 512/512 bytes
Disk identifier (GUID): 46236-STUFF-77
Partition table holds up to 128 entries
Main partition table begins at sector 2 and ends at sector 33

First usable sector is 34, last usable sector is 11721045134
Partitions will be aligned on 2048-sector boundaries
Total free space is 3181 sectors (1.6 MiB)
Number  Start (sector)    End (sector)  Size       Code  Name
   1            2048     11721043967   5.5 TiB     8300  Seagate6T

Command (? for help): r
Recovery/transformation command (? for help): i
Using 1
Partition GUID code: 0FC63D-STUFF-E4 (Linux filesystem)

Partition unique GUID: E72007-STUFF-46
First sector: 2048 (at 1024.0 KiB)
Last sector: 11721043967 (at 5.5 TiB)
Partition size: 11721041920 sectors (5.5 TiB) 
Attribute flags: 0000000000000000
Partition name: 'Seagate6T'
Recovery/transformation command (? for help): x
Expert command (? for help): v
Caution: The CRC for the backup partition table is invalid. This table may
be corrupt. This program will automatically create a new backup partition

table when you save your partitions.

Problem: The secondary header's self-pointer indicates that it doesn't reside at the end of the disk. If you've added a disk to a RAID array, use the 'e' option on the experts' menu to adjust the secondary header's and partition table's locations.

Problem: Disk is too small to hold all the data!
(Disk size is 3131110576 sectors, needs to be 11721045168 sectors.)
The 'e' option on the experts' menu may fix this problem.

Problem: GPT claims the disk is larger than it is! (Claimed last usable
sector is 11721045134, but backup header is at 11721045167 and disk size is 3131110576 sectors.

The 'e' option on the experts' menu will probably fix this problem

Problem: partition 1 is too big for the disk.

Partition(s) in the protective MBR are too big for the disk! Creating a
fresh protective or hybrid MBR is recommended.

Identified 6 problems!Command (? for help): x

Expert command (? for help): e

Relocating backup data structures to the end of the disk

Expert command (? for help): w
Warning! Secondary partition table overlaps the last partition by
8589933425 blocks!
You will need to delete this partition or resize it in another utility.
Problem: partition 1 is too big for the disk.
Aborting write operation!
Aborting write of new partition table.