"Legacy" blog?

Sadly, I have much to say but don't know how to use the format. I am posting this because I got a note from google that my "legacy" account will vanish if I don't set up a new account. Have no idea how to do that. It took me 12 times to get into my own blog. They sent me my username which is exactly what I had been entering and used today to get in but when I put that into where they want you to sign up for a new account they say the username isn't associated with any account. (How's that for a run on sentence Sister Grace Aurelia)? Don't get it. Hope I don't lose this blog, because I want to start using it again.