UpdraftPlus Update – moving from Premium to Free?

I have inherited a WordPress site that I now manage. The site uses UpdraftPlus Premium to back up the site to a Google Drive, but this has expired so I am not able to update the plug-in. I want to start using the free version of UpdatePlus, but I cannot figure out how to do so. When I attempt to update UpdraftPlus, it fails; I do not have log-in details for the UpdraftPlus account so I cannot renew via the website (and do not want to continue to pay the Premium fee). Please advise how I can download the free version of UpdraftPlus if I already have an expired Premium version installed.