Your issue is off topic in the Universal FW Patcher thread, as the Montana 610 does not need any FW patching to use the CN North America NT map. I therefore moved the particular posts to the CN North America NT 2017.30 thread.
All you need to do is:
- Copy the (locked) CN North America NT map img file from the zumo 660 to your PC desktop.
- Download and save gimgunlock+mapsigpatch to your PC.
- Place a shortcut to gimgunlock+mapsigpatch on your desktop.
- Drag & drop the (locked) img file from your desktop onto the shortcut to gimgunlock+mapsigpatch.
- The img file will be unlocked on the spot in a matter of (not even) seconds.
- On a microSD, create a root folder named Garmin.
- Drag and drop the unlocked img file from your desktop into the folder Garmin.
- Not that it should be necessary, but to be sure, rename the img file on the microSD to gmapsupp.img.
- Place the microSD inside the Montana 610 and the map should be recognised and loaded.