How do I retrieve deleted text messages

Go to Settings > Your Name, Apple ID, iCloud, iTunes & App Store

Tap iCloud

Are Messages turned on?

If yes, you can't restore deleted messages.

If no, if you have a backup made from before you deleted the messages, you can restore the phone from that backup. But be advised the phone will be restored to the date the backup was made, meaning text messages sent or received after the backup was made will be gone.

If they are not in your iCloud account or present in a recent back-up, they are probably gone forever.