downloaded Thunderbird. had it before, about a month ago. made donation, but tried to install on Windows 11 and I don't know what password to use. i tried Windows PIN, old Mozilla and Firefox password

It's asking for your email account's (Gmail, Yahoo, AOL, etc.) password, not your computer's or Mozilla's password. That is, you must already have set up an account with an email provider before you can set up Thunderbird to manage email at that provider.