@ twerppoet, I think he wants to transfer the Kindle books from the iPad to the iMac.
And to do that you can go to Amazon.com and download the Kindle App for Mac and you will need to register it with the Amazon account used with the books, and you will be able to read them on your computer.
Also, Amazon remembers every book you've downloaded. As Twerppoet said they are in the archived section. So if you have to replace your iPad you can just log in to the new one and re-download the books.