Upload more pictures. Some of those were removable. Not sure about this model.

WD and Toshiba portable drives have USB soldered on. Seagate portables still have a SATA interface.

I'm guessing there's no SATA beneath all of this?

Correct, these are native USB drives.
You are stuck with this so you might as well put it back in the case.

looks like it. you can still use it in a nas. just connect it to a usb port instead of sata, it should be fine except possibly limited SMART Info.

Most external 2.5" drives do not have sata connections. Only the 3.5" drives are a reasonable safe bet, and it's still not a sure thing. Best to look up the drive before purchasing.