where is my music? i lost my music in the library

Turn on Sync Library. Go to settings>music>sync library. According to Turn on Sync Library with Apple Music - Apple SupportI, "f you don't subscribe to Apple Music or iTunes Match, you won’t see an option to turn on Sync Library. If Sync Library is updating or turned off, you'll see a message at the top of the Library tab in the Apple Music app."

I hope that helps!