How do I retrieve messages in I cloud?

I am afraid that once you delete a message using Messages in iCloud, it is gone for good. With Messages in iCloud, when you delete a message, attachment, or conversation on one device, it deletes from all of your devices. This can help free up some space in your iCloud storage, while keeping the rest of your conversations up to date across your devices. Once you delete a message, you can't get it back.  For more info, see:

How to delete messages in iCloud - Apple Support