Cant access TIME Machine due to unusable external backup being programmed into computer

What do you mean by "changed locations"?

What kind of NAS were you using?

In order to troubleshoot this kind of thing we need *lots* of details, remember we can't see your machine.

It might be easier to get a new external hard drive and start over with Time Machine.

Backup disks you can use with Time Machine - Apple Support

Your friend set up network-attached storage on a Raspberry PI server with a Time Machine server, based on the (cute) name.

Here is an example:

… https://www.raspberrypi.com/tutorials/nas-box-raspberry-pi-tutorial/

… https://www.rogerfrost.com/set-up-a-timemachine-backup-folder-for-mac-on-an-openmediavault-server/

What to do here? Remove ➖ the NASBerryPi Time Machine device, as that is no longer accessible to your Mac.

Here is how to remove the device: Change Time Machine settings on Mac - Apple Support

To get Time Machine backups going again… You will want to acquire an external hard disk, or an external NAS if you have the budget for that (either home-built as previous, or Synology or some other commercial option), connect it and turn it o, and then add ➕ that as a new backup target in the Time Machine settings. The external hard disk is the easiest to add, and capacious hard disks are widely available for comparatively little. (Your data is worth more.)

How big? Go for a disk with double or better triple the Mac storage to be backed up.

Why have backups? We see too many cases of data loss.