Open the Messages app
Tap Edit or Filters
Tap Show Recently Deleted
Select the messages you want to recover
Tap Recover
Check the Recently Deleted folder in Messages
Restore from an iCloud backup if the messages are not in Recently Deleted
Restore from a computer backup if you previously backed up your iPhone
Ask the other person in the conversation to resend the messages
Check other devices signed in with the same Apple ID
Use a third-party recovery tool only if you trust it