Hi. It might pay you to review both documents again. Catalina and later encompasses Monterey. You cannot install the Music app, on anything, it comes as part of macOS 10.15 and later. The Music app should be able to convert iTunes libraries, however for reasons unknown the version of Music in Monterey is particularly bad at it. Ideally it will also convert libraries from all older versions of iTunes, but in fact it will only work with one produced by iTunes 12.9.5.5 (the version on Mojave) or a Windows version of iTunes that was released prior to the version of Music included with the particular build of macOS. Since you have Mojave your iTunes Library.itl won't need to be updated before it can be converted to Music, but Monterey cannot do it. It needs to be done in Catalina or Big Sur, and then the resulting Music Library.musiclibrary database can be used on your updated machine. If you'd like me to help you can find my email in my profile here. I've done around 120 of these by now. Email your .itl or a link to it in a cloud service and I'll send back the converted file along with additional advice on how to use it, and then how to move your library into the modern layout.
Alternatively you might be able to download and install Catalina, and access Apple Music to convert your iTunes library, before upgrading to Monterey.
tt2
