In general, Music is not backed up.
Purchases from the iTunes Store can be re-downloaded from the store if still available, and any music obtained from other sources such as ripped CDs and other music stores, should be kept on a computer and can be synced from there directly. click here ➜ Redownload music - Apple Support
and click here ➜ Use iTunes to sync your iPhone, iPad, or iPod with your computer - Apple Support
Music added to your library from the Apple Music subscription service should automatically re-populate on the new iPad in the Music app when logged in with the same Apple ID as before but would need to be re-downloaded to the device manually.