If there is anything left, check c:\(yourname)\appdata\romaing\lthunderbird\profiles to see if there is a Mail folder or Local Folders.

To Locate via Thunderbird Help > More TRoubleshooting Information In 'Application Basics' - half way - Profile Folder - click on 'Open Folder' New window opens showing contents of profile name folder

Exit Thunderbird now - this is important.

Click on 'Mail' folder It will list all POP accounts plus 'Local Folders' mail account.

Right click on 'Local Folders' folder and open in a new window - leave as you will need this later.

Back in 'Mail' folder...click on the pop account name which you just removed - it should still be in that location - to see contents.

It will contain mbox files (no extension) they will have same name as folders and they contain emails. It will contain files with .msf extension - they are index files - do Not contain emails. You may see fodlers with .sbd extension. These folders mean you had sub folders and they contain mbox files.

Copy all the mbox (no extension) files and also all the folders with .sbd extension.

Paste all the copied files and folders into the 'Local Folders' mail account folder.

See image below as guide.

Then when you start Thunderbird, you should see all the folders and emails in the 'Local Folders' mail account.