My old compaq computer had Linux mint 17.1 on it when the hard drive suddenly failed. I had backed up each week to an external drive. As a replacement I got a Dell studio 1749 on which I put Linux mint 18.3 with a stronger password. When I try to restore the backup the computer doesn't see it. I can get to the folder in the backup drive but it is blank. My knowledge of Terminal is limited to copy and paste. Can anyone help.