Switch from Basecamp Mac to Basecamp Windows - move data

Current Mac OS Sequoia does not mount my Garmin  396, so updates and using Basecamp about impossible.  

Less trouble to mount on windows machine.  Have extensive routes and waypoints in my Mac Basecamp.  

Is there a format to bring from Mac to Windows.  

I have read of issues going in reverse direction, from Windows to Mac, due to incompatibility of format of data exported from Basecamp Windows.  

Any advice or experience out there?