The messages were deleted from the IMAP server when they were deleted on the phone, so when the folder synced with the server in the new profile, it synced with an empty folder. Copy the mbox file from the backup, the file named Archive that has no extension, is large, and is stored with an Archive.msf file, into the Mail/Local Folders location of the new profile, with TB closed, then restart TB and find the Archive folder under Local Folders in the Folder Pane.

There is a way to copy (upload) the messages from Local Folders to the IMAP server, if necessary.

I will try that. Thank you!

OK this is weird... there is no Archives.mbox, only the msf. However, instead, I closed Thunderbird, copied the imap folders into the Local Folders and like 70% show up when I reopen Thunderbird. Any idea why? I tried repairing the folder, too.

The Archives mbox file has no extension, i.e. it's just Archive, not Archive.mbox. Ignore the .msf file when copying into Mail/Local Folders. Look for mbox files also in sbd (subdirectory) folders.

Right. Ok got it. I only have the Archives.msf. There is no other item called Archives anywhere.

I found other mbox folders in subs but copying them over to the current profiles local folder still isn't making them all show up.

If you just have the .msf file, it means the folder was set to download headers only, not message bodies. The setting is in Synchronization & Storage in Account Settings.

If an mbox is corrupted to the point where it doesn't appear in TB, you can try one of the repair utilities that are found through a web search.