Mail Folders on my MacBook Disappeared

I'm on a MacBook 12", early 2016.

Running Mojave 10.14.6.

In Mail, all the folders and emails in the "On My Mac" section disappeared.

I have no idea what happened. I believe they were there yesterday and this morning they were gone.

I have 3 gmail accounts and 1 iCloud account.

I did a Time Machine back up during the night (early Thurs AM 5/7/20). But I think everything was fine after. I didn't notice anything missing, but I wasn't specifically looking either.

Help!