Open the Messages app
Tap Edit in the top-left corner
Tap Show Recently Deleted
Select the messages you want to recover
Tap Recover
Tap Recover Messages to confirm
Check the Recently Deleted folder in Messages if available
Restore from an iCloud backup if the messages are not in Recently Deleted
Restore from a computer backup using Finder or iTunes if you have one
Contact your carrier if the messages were SMS and you need account-level records
Ask the sender to resend the messages if recovery is not possible