If you deleted folders, the folders should be in your trash and you should be able to move them back where you want them by clicking and dragging or by using the right-click menu.

Thank you. I can see the messages there in the trash, but they are not organized into the folders that I had created. So....I suppose I can make the folders again and move the messages back in there but would prefer not to take the time if there's an easier way.

Do you have a back-up?

Yes, I believe it's backed up in the cloud though I don't know how to find what's there.

I should have asked earlier: Were these local folders or server folders?

When I delete folders, the whole folder goes into the trash.

You will want to learn more about what is backed up and how to access it. You are looking for your Thunderbird profile. On a Mac, it's in the Library folder of your user folder. I do not know where it is on Windows.