Just use routable open street maps they are free no need to make maps.

Download the map or maps and put it in the \Garmin <--------folder
Then go to the settings app:
:Map Settings
:Map Infomation
And turn on the map or maps you installed.

If you are using official Garmin maps like the City Navigator Europe NT map you will need the unlock file also.

Spoiler: Free routable open maps
[Only registered and activated users can see links. ]