How Can I restore deleted text messages that I have backed up in iCloud
How to restore a deleted iMessage from my iCloud backup
You restore the iPhone to your iCloud backup. You cannot restore selectively. It is either all or none. If you are using iCloud Messages, in other words, if that switch is on, then you are not backing up to iCloud, you are syncing messages in iCloud and if you deleted one, there is no recovery.