Restore iMessage thread with iCloud for Messages enabled

I apparently deleted a message thread over 30 days ago, as Recently Deleted does not contain what I am looking for, however I validated the missing content was present on a device I had offline. After putting that device online and allowing it to sync with iCloud the thread has been deleted. My objective is to restore this thread. I have local iOS/iPadOS and Time Machine backups with this thread. What is the easiest method is to merge this missing thread/content into my current iCloud for Messages database?