Hello 9823,
Where are these playlists you're talking about? Were they on a previous computer? If so, then you'll want to move the iTunes library over to the new computer.
Move your iTunes library to another computer
If you no longer have the computer that the playlists came from, then you'll need to recreate them. You can sync items to your phone from the iTunes library with these steps: Use iTunes to sync your iPhone with your computer
If you're using the Apple Music service, then you can set up the library sync so your libraries automatically stay up to date without having to connect the devices.
On the computer:
1. In the iTunes app on your PC, sign in to the iTunes Store using the same Apple ID that you used to set up iCloud Music Library on the first computer.
2. Choose Edit > Preferences, then click General.
3. Select the iCloud Music Library checkbox.
On the phone:
1. Make sure that your iPhone or iPad is signed in with the same Apple ID that you use with your Apple Music subscription.
2. Go to Settings.
3. Tap Music.
4. Turn on Sync Library.
Use Sync Library to access your music library across your devices
Cheers!
