Restoring deleted messages by syncing devices

Hello, I hope you can help me. I accidentally deleted a conversation on my iPhone. My iPhone is synced through iCloud with my iPad, so the conversation was deleted on both. I've since started a new conversation with the person. Messages on my MacBook Pro are not synced with iCloud, so I still have the old messages in the conversation, plus the new ones.

I would like to restore the full conversation that is on my Mac to my iPhone/iPad. How can I do that? I really don't want to risk losing the old messages.

Thanks very much in advance.