This can be problematic if you have a Mac with an SSD that has limited storage, and had previously kept all your media files on an external location, as macOS tries to move some files when you upgrade. Instead of them all being in an iTunes Media folder, which can be on your Mac or on an external or network drive, some of these files will be moved. One problem that users will encounter, when they first start working with these new apps, is where the files are stored. (Previously, Books only managed ebooks it has inherited audiobooks from iTunes.)
Books will hold your ebook and audiobook library.TV is the app you will use for your movies and TV shows.
In addition to the Music app, which is more or less the replacement for iTunes, there are three other apps that manage media files: Since the release of macOS Catalina, Apple has removed some of iTunes’ media management functions and created new apps. Software & Apps How to manage media files in Apple’s new Music, TV, Podcasts, and Books apps
