To update your portable Nextar navigation system, you need to have a Nextar GPS and SD card map upgrade. First, get the serial number of your GPS and go to nextar.com to order for the update. Remove the existing SD card and insert the card with the maps upgrade into the SD card slot. Next, you reset the unit by pressing the reset button. Finally, click the 'navigation button' to automatically update the GPS.
Nextar went out of business so, anyone with a Nextar GPS unit is screwed as far as ever finding an update. So suck it up and buy another GPS unit and I suggest finding one from a company that has been around for a bunch of years, as an example you might try TomTom or any one that is still in business and has been for several years.