Hi, @scojophoto-mac-c.
You have two ways to open and migrate your file. It's my pleasure to share them with you.
The first option is to upgrade your QuickBooks Desktop for Mac to a newer version. The QuickBooks Desktop for Mac 2016 is a version that's already discontinued and the version is incompatible with the new macOS version.
The second option is to go back to the old operating system (OS) while we're working on Big Sur. You can reach out to the Macintosh Technical Support Team to revert your OS to the previous version.
Once you're in the old OS, you can create a backup of your company file to ensure you'll have an original copy that you can restore in case of data loss. When done, head to the Download Center at this link to get the latest version of QBDT for Mac.
You can check out these links for your reference in backing up and restoring your file:
On the other hand, you can visit this link to stay in the loop whenever any updates regarding the compatibility of Big Sur to the other versions of QuickBooks for Mac are released: Intuit’s support policy for QuickBooks for Mac running on macOS 11 Big Sur.
Lastly, here's an article you can open to know more about converting a QuickBooks Mac Desktop file to QuickBooks Online.
If you have any other questions about QuickBooks Desktop for Mac, please let me know by adding a comment below. I'm always here to help. Have a good one!
