you for reaching out to the Community regarding your issue. You should be able to load the backup when making a new file. The option to start from a Quicken for windows file will be available. You can start a new file by going across the top to file > new if you have an existing mac file. If it's your first time launching the Mac program it should ask if you have an existing file as well to convert.
If you have any questions or you're looking to use Quicken for Windows on your Mac please let us know.