7 TB is a lot of data. Proceed cautiously and think everything through before doing anything. I am almost afraid to ask: is this data backed up? It's important to back up anything important. There are automated programs that will do this (including Apple's free Time Machine).
It sounds like possibly the drive was forcibly ejected due to the cable dislodgment and since it was in the middle of modification to the file system, the file system (catalog) MIGHT have been corrupted.
If the external drive is HFS+, I would suggest looking seriously at Disk Warrior. One problem with file system repair tools is if they don't work, one can create additional damage or even make the entire disk unrecoverable, a total loss.
Disk Warrior is a bit different. It recreates the entire file system from scratch. This can take a long time (especially for 7 TB), because this is analogous to driving up and down every street in a city and re-recording where every house and address is located. And imagine each house is actually in pieces in different parts of the city. That is what hard drives are like. But Disk Warrior does not try to "repair" the file system, it recreates the entire thing. After it completes this task, it presents you with a listing of files and folders as indicated under the existing file system, and side by side shows the new candidate file system it presents for you to approve. Only after you approve the new result, does it actually go and replace the old one. "DiskWarrior's patented preview feature lets you see how your disk will appear after it is repaired, but before any changes are made. You can even compare your disk in its damaged state to its repaired state." Then, if you choose to proceed (and if you have concerns you can simply say "no" and then no changes are applied), Disk Warrior claims it uses a "fail safe" method to replace the old with the new file system, although I don't know what that "fail safe" claim means exactly, I think it uses a method that is resilient to loss of power during the process, for instance.
I have Disk Warrior but have not needed to use it for years. However when I did use it, it restored a drive that was completely unusable, not one single file could be retrieved, and afterwards it was all back, 100%. So I know that under some circumstances it can work very well. When it works like this, it is truly like black magic when it restores an entire drive. But if there is hardware damage, none of these utilities may work.
If the external drive is a spinning mechanical drive, there are some very expensive things you can try that may work. Recovery companies will take the platters apart and try to read all the individual bits (ones and zeroes) off the platters. This is expensive because it is done in clean rooms and very labor intensive. With 7 TB of data, it will be very costly, possibly many thousands of $. What is recovered might be fragments of files. Probably only to be pursued if the data lost is priceless and you have to have whatever can be salvaged.
P.S. I would contact Sandisk because they may have proprietary recovery software that works better with their hardware. They do have such tools for their camera cards.