I have a US version of Quickbooks for Mac as it wasn't available in Canada at that time. It crashed on me when I updated to Big Sur. How can I get it running??

Quickbooks mac version 2016.  I have called quickbooks numerous times and been unsuccessful with anyone that can help.  I am currently using quickbooks online.  I even tried myself to download a desktop trial version and it crashed when it tried to upload the 2016 files it did find it the first time.  Then after that it just crashed.  It worked fine until I updated my mac with Big Sur.  Was hoping I could find a patch for this error when getting the newer software with apple.  No luck with that either.  So important for my business that I have these files available.  Hoping someone can assist me.