Google or Duck the search phrase "backup mojave". On page one you'll see an article titled "How to Backup & Restore macOS Mojave". I suggest you start there if you wish to properly back-up your system.
For better data portability you may import your iTunes data into Spotify and use the free streamexport.com website to connect with your Spotify account and, from there, export CSV files representing your entire library.
For better data portability you may import your iTunes data into Spotify and use the free streamexport.com website to connect with your Spotify account and, from there, export CSV files representing your entire library.