Changed AZW4 book extension to mobi and lost my book cover

I have an AZW4 book. In order to load it onto my iPad Air, I had to change the file extension to .mobi. The iPad reads the book as it should with all the Kindle app features. My problem is that when I changed the file extension to mobi, I lost my book cover. Is there any way to get the book cover to properly show in the Kindle app? The book I have is in two parts (textbook). And I can't tell which part is which without the covers showing, unless I blindly click on one of them.

Anyone know how to solve this frustrating problem?