A:Answerif your books on in Amazons cloud, you can re-download them once its registered to your account. if they were only on the old Kindles and not backed up to your PC, unless you can mount the Kindle and move the files over, its possible they are lost .... If all else fails, you could contact Amazon's support to see if they can salvage the files.
A:AnswerAmazon apps are very limited go to apps and type in the app up on amazon fire if it does not say amazon app when an app come up u will have to bookmark the website