Hi saabaero1,
The steps you'll need to take will vary depending on the source of the tracks in question.
If these were songs purchased from the iTunes Store, see Redownload music for the steps to redownload those purchases.
If synced from a computer, use Sync music between your Mac and iPhone, iPad, or iPod touch to sync those tracks from your Mac with updated software or Use iTunes to sync your iPhone, iPad, or iPod with your computer for syncing with a PC or older macOS version that does not have the Music app included.
If you're an Apple Music subscriber then visit If songs are missing from your music library after you turn on Sync Library for songs in your Apple Music library that are missing.
If something else, provide additional relevant details on the situation to aid future replies in providing appropriate suggestions.
Regards.