Whenever you restore backed up files, always use the same version of Backup (or later) that was used to create the backup.
For example, if you created a backup using Backup 3.1, do not try to restore backed up files using Backup 3.0.1.
If, on the other hand, you created a backup using Backup 3.0.1, you can use any version from 3.0.1 or later to restore the files.
It is recommend that you always update to the latest version of Backup before you attempt to restore a backup.