Hi. I'm Brian and I'll try to help.
When you delete a folder in classic Outlook, it becomes a subfolder of the Deleted Items folder. That folder should have a > symbol to its left that you can click to see the subfolder. You can then drag the folder back to the folder where it used to be located. If you've emptied the Deleted Items folder, however, the folder you deleted is gone for good unless you made an offline backup of it.