Your OS crashed... as your Thunderbird "Local Folders were on the same hard disk, what did you do with the disk? Any chance of recovery depends on what you did and how you recovered from the crash so be specific.

Load them from your backup.

What backup? I don't back up my e-mail?

Maybe you should after losing them twice. https://support.mozilla.org/en-US/kb/profiles-where-thunderbird-stores-user-data

I started using Thunderbird as a favor to a friend who was trying to build community. Yes this is the second time I've lost most of my e-mail, all of my folders. And each time I've asked for help, I've received arrogant and condescending responses. Obviously I'm not the user you are looking to support. Simply because I'm not a tech nerd, is no reason for your lofty tone. I assumed that my e-mail, folders and mail, were stored on a server and that by logging into my account everything would be there. Imagine my surprise when that wasn't the case. I use Yahoo as a back up and when I logged back in my folders were all just as I left them. I'll be leaving Thunderbird because of your horrible service. I'm sure you could care less, which makes it the right decision for me. Best of luck keeping subscribers like me. You're going to need it!

It was advice. Get over yourself.

Martinigal said

I assumed that my e-mail, folders and mail, were stored on a server and that by logging into my account everything would be there. Imagine my surprise when that wasn't the case. I use Yahoo as a back up and when I logged back in my folders were all just as I left them.

You assumed incorrectly obviously, the folder is called Local because it is just that. But I made that clear yesterday. Given you have not answered my questions I get no option but to give up.