Every Garmin GPS has a unique Unit ID (10-digit number) , the Unlock Code will only unlock the maps with your GPS ID. Use one of the following methods below to find out your GPS ID (Unit ID):
a. Nuvi/StreetPilot:
Go to Tools->Settings->System->About
b. GPSmap 60/76 series:
Press Menu twice, go to Setup->System then press the Menu button and select Software Version
c. MobileXT:
Go to Settings->System->Remote GPS or Tools->Settings->About (depending on version)
d. GPSProxy 2.2c:
Go to Menu->About or Que: Go to Menu->About Garmin Que
e. Mapsource:
Make sure your GPSr is connected to your PC then go to Utilities->Get Unit ID