Two Hds Becoming Unallocatedafter Being Moved Through Customs

I had 2 functioning desktop computers before I put them in boxes for a moving truck going from the US to Canada. One was an older reconditioned gateway windows 7 OS was on the normal HD now it does not boot at all. I've tried multiple paths to get it fixed and each time I reach a point where it works in the tutorial but not for me. I've only tried different methods on the older comp thus far I created a windows 7 boot disk USB and tried to use the fix option rather than format. With the help of some sites I went into the Bios, command prompt, and tried fixdisk, and boot sector repair to my limited knowledge I don't think I tried anything heavy handed.

The newer comp is windows 10 I have a 4TB backup HD that went unallocated. Thankfully the 500Gig SSD was where I put the windows 10 OS. I'd like to get the data and the files back if possible. Recuva was the best recommend program to try and use on one site, if that is even the best one can handle only up to 3TB. The older comp I don't even know how to go about trying to fix it I'm also not quite sure how big the HD is there are some tight corners and I haven't yet found the way to get one of the mounting screws off, I realize it might be a sliding box HD storage but this has been defeating me and anyone who tries to help for a couple months and it's hard to work up the energy to even try anymore. That comp also has an 250 or 500 gig SSD but I honestly no longer remember which had the OS on it. Although in typing this I think I had a comp store swap the OS to the SSD.

Part of me wonders if some sort of moving Truck X-ray did a number on them somehow. I also wonder if when I was having a monitor issue after arriving I may have powered off during a windows update. Regardless I usually have one computer up for what I'm working on while the other is my reference computer. I've never been a fan of multi-monitors on the same computer. The older comps windows 7 functions are familiar as well and it handles some tasks better for me.

I do know both HDs are Seagate BarraCuda brand. The windows 7 boot "disc" is on a 16 thumb drive. Some thing that might also be helpful a cyber Monday 500gig SSD and mounting bracket arrived today.
Thank you in advance for any help.