To get your subfolders back, try rightclicking the account, and then click subscribe. That may do it.

I can't find a subscribe button anywhere.

In left folder pane, highlight the account, then right-click and you should see 'subscribe' as an option. See attached screenshot

Found it. I ended up creating a new "account" in T bird. I set the previous account as a POP acct. This time I set it as an IMAP acct. I got a new email but my folders still haven't migrated.

I think this solves the 1st part so thank you very much, sir. This brings me to a new question along the same line. How do I delete the original POP version?

Go to tools>accountsettings - highlight the POP account in left side - scroll down slightly further to 'Account Actions' - which is a dropdown menu with option to delete account.

I'm not seeing Account Actions anywhere.

Please do a screenprint of your tools>accountsettings page, with account specifics collapsed.

Edited

Nevermind. I'm a moron today. I didn't look far enough down the page. Let's call this the 7th Monday of the week.

I'm glad you resolved this.

Yes, sir. Now, if I can get all of my Gmail folders back in T bird, I'll be all set.

Closed/reopened T bird and all of the folders are there now. Thank you again, sir!

Much better now.