Did you or can you back up those files to a USB flash drive? If so , you should have no problem restoring those files to the old software... But first you have to reinstall the old software on your new computer, and then restore the client files for that applicable years software... Then after you install the 2021 software, you can just transfer the files from the 2020 software to 2021 software, as usual... this has worked for me in the past, but I'm not sure if this can help you with your unique situation...just my opinion... Good luck