Your email password is between you and your email provider and I am sure they have a way to reset it on their website. Check their help page.

I got into my account, but cannot figure out how to retrieve my old message and folders. Are these automatically backed up somewhere?

If you back them up.

What type of account were you using on the old computer. POP or IMAP. What did you setup on the new one?

I didn't back up manually, I thought it was an automatic backup to the T-bird server. I was and still am using POP for my emails. Thanks!

Does Microsoft backup all your word documents? Does adobe backup your PDF files?

The short of it is if your account is IMAP, then a copy remains on the server at your mail provider aqnd storasge is limited to the quota of disk space they provide. For pop it is stored on your local computer and it is your responsability to manage your backups.

So if your reinstalling because you got a new computer, and you have access to your old then there is hope for a transfer. If you simple tossed it or the hard disk failed then the game is over.

What server would that be? Thunderbird is email client software that runs on YOUR computer. Email providers have servers. You can check with your provider for any backup they might have. If you are using POP the normal operation is to download messages to your local computer drive and remove the copiy on the providers server. If your old drive is still operational then someone might be able to recover your data from it. Otherwise it is up to you to make backups.