How to retrieve I messages from I cloud

If you are syncing Messages with iCloud, they are already in your device and they are no different than what you would see in iCloud.

If you included text messages in the iCloud backup, you have to restore the backup to see any text messages that you may have deleted from your device but are still in the backup. When you restore a backup, you overwrite the contents on of your device and fill it with the data in the backup.