By posting here in the forums.
The backup would be from when the old servers were taken down, basically it would be the same state as when migrations was started in December. To use that backup we'd need to wipe the current DirectAdmin account and redo the transfer using said backup. I have not verified they are still available as I'm not logged into that system right now, though last I heard there was no hurry to clear that space up.
Have you made any changes on your account since the migrations took place? If so you would need to make a backup of those for safe keeping on your local computer so you can re-apply those after the restore is done.