With new updates in iWork (Keynote, Pages, Numbers) you can now add 3D files (USDZ) to documents. Mike Sammartano is an Apple Distinguished Educator and Apple Learning Coach who shares amazing free resources for education. He put together a video to help users learn how to use and animate USDZ files in Keynote.
You can download the file for free: Keynote for iPad/Mac: Sample 3D USDZ Models
Also, if you're looking for different USDZ files, this Padlet has a ton of options from Using Tech Better.
Keynote
Pages
Numbers