If the account is POP, you can copy the message folders to Local Folders from within Windows File Explorer to retain the messages. If IMAP, you would first need to verify that all folders can be accessed offline and then click File>offline>download. After confirming that you have them all, you could do as above for POP.

I was able to go online to [email protected] and it is all there. I don't know if that means POP or IMAP. I have used 88% of 2300 mb so I am guessing this is a lot of data. I just want to make sure I do this right so I don't lose anything. When I "download" where is it going? Are you allowed to contact me directly via phone so you can walk me through this at some point? Thank you for your quick initial response!

I am assuming you still have the account on thunderbird. The download will go to the profile, which I assume is the default on drive c. The actual location can be determined by clicking 'server settings' and viewing the bottom row that shows local directory. That would be the directory of the account and the message folders would be subdirectories of that (e.g., ...imapmail\<youraccountname>\INBOX and INBOX.msf) The download does not destroy anything, so you won't break anything. Verify that you have it all after the download, as it's possible it may not all download. Then exit TB and COPY the message folder to the Mail\Local Folders folder in the profile (NOT the imapmail folder). BEFORE STARTING, click 'synchronization&storage' advanced tab to confirm that the folders may be downloaded. You need to individually download each folder.