My External hard drive fell and not showing up on Mac
The drive enclosure may be broken, but it could also be the drive itself, being the logic board or head. It's more likely the drive is broken if it was powered on when it fell. Since it's your backup drive, you hopefully haven't lost anything critical. I'd start thinking about getting a second backup drive to reduce your exposure to loss.

Most USB externals are fairly easy to take apart with a screwdriver, and just have a standard SATA drive inside of them. If you have a SATA to USB adapter you can test it, or even better is to connect to an internal SATA to verify S.M.A.R.T. etc. However a 1TB drive is pretty cheap now, so you might just replace instead of trying to repair.