Unfortunately, Garmin does not offer free map updates.
You can attempt seeing if there are any available updates by going to https://my.garmin.com/maps/updates.htm and entering the serial number of your device. This will let you know if there are any possible free mapping updates.
If you are getting a message informing you that your Maps are outdated, you can try installing the latest Firmware/Application update for your device. Go to http://www8.garmin.com/products/webupdater/howtoinstall.jsp to download and install any firmware/application updates for your device.