1. Make sure you are signed in to the correct Apple ID. Tap on the profile button on the top right corner and make sure your current account is the one you're expecting.
2. Check the Music Library section. Tap the Library button on the bottom of the screen and make sure the Songs category is selected.
3. Use the search function. Tap on the Search bar at the top of the screen and enter the name of the song, album, or artist you are looking for.
4. Check your iCloud Music Library settings. Tap Settings (the gear icon) > Music and make sure iCloud Music Library is turned on. This will ensure that all your songs are synced across your devices.
5. Check the Show Apple Music catalog setting. Tap Settings (the gear icon) > Music and make sure Show Apple Music catalog is turned off. This will ensure that you are not seeing songs from the Apple Music catalog instead of your own library.
6. Check the iTunes Store. If you purchased the song from the iTunes Store, you can try searching for it there. Open the iTunes Store app, tap the Search button, and enter the name of the song.
If you still can't find your songs after following these steps, you can try contacting Apple Support for assistance.