I'm glad to hear that you have the right maps in mind.
When dealing with an update for your Garmin device, it is best to simply download, install, and use Garmin Express.
and (if you have a Windows PC) click on the big blue Download button at center bottom of the page. (If you have an Apple, click on the nearby Download for Mac link.) And download Garmin Express' installer to your computer, save it, then double-click upon it to install Garmin Express.
Then start the program, Garmin Express. Then connect your Garmin device. Then use Garmin Express to update your device.
See if that helps move the maps to the device. It might.
(If it doesn't, let me know, and I will instruct you as to how to get the maps onto the Garmin device, if you can tell me what the file types are, and what website they are from.)