Mail lost its brains. How do I rebuild from backup?

This is odd. My Mail app suddenly lost everything. It doesn’t remember any of my email accounts except the icloud account. Not too worried as they were all (well, most) imap but I had many folders in On My Mac folder. But I have complete backups, Time Machine, Backblaze, and SuperDuper.

Not sure where to find everything to restore, though. Could use some tips.

As for the cause, I was trying to restore some apps on my daughter’s phone using iMazing, which required I sign into my wife’s icloud. Later, saw that my iCloud account was no longer connected and it would not recognize my password; I restarted and finally it logged in. All very odd. But now that it’s back. my Mail came up empty and it downloaded all the icloud mail but nothing else and none of my usual accounts are listed.

Also did some cleanup thing using CleanMyMac, that may have been what did it.

Later: I tried to change my icloud password as a precaution but could not do so on the Mac. Apple thinks this Mac’s icloud account is new! Changed it using my iPhone but thought it an interesting symptom.

I’m pretty puzzled…Ideas? My main question is: What do I have to pull from backup to get Mail's data back?

TIA...