To convert maps for the Mac you can use Garmin MapConverter:

[Only registered and activated users can see links. ]

◦ MapConverter converts maps and unlock codes on your Windows PC to the Macintosh format.
◦ View instructions on migrating Garmin map products from Windows to the Mac here. (PDF file- 245KB)
◦ Please send issues to [Only registered and activated users can see links. ].
◦ Download and install the MapInstall/MapManager package to your Mac to complete the migration.