REGISTER or login:
The question makes no sense. A DVD has no reason to be saved as a .QBB file. It's possible that there was a .QBB file that was stored on a DVD, or someone could have manually used a .QBB extension after creating an image of a DVD.
But if a DVD really was somehow saved as a .QBB file, you'd have to ask the person who did it what the proper procedure would be to handle it.
And if you simply have a real Quickbooks backup file, just run Quickbooks and take the Restore menu option.