Restore deleted messages

Unfortunately, if your messages were synced with iCloud, it will not be possible to recover them. When you delete something on your phone that is synced with iCloud, it disappears completely.

If your messages were not synced with iCloud but were located locally on your iPhone, then you can try to restore from an iCloud Backup from the time they were available on the phone.

You can read here how to restore from an iCloud Backup:

Restore your iPhone, iPad, or iPod touch from a backup - Apple Support

Can I restore deleted messages on my iPhone?

Possibly, but it's complicated at best.

The iPhone would have had to be regularly backing up to a Mac......AND......the Mac would have had to be backing up regularly to another external hard drive using Time Machine.

No need to go into further detail unless both of these conditions existed.