fix auto-fail backups?

so it's a simple mint install. home desktop install, no VMs or anything complicated. for whatever reason the mint backup program wants to back up to /media/tom/(long string of gobbledegookhere), this directory does not exist on my machine. it appears to start existing if I plug in a USB drive. I can't find anyplace to config the backup program to use an existing partition. What's up with this?

oops, error message is "permission denied"