I plugged my gps into my computer and deleted all the info on it how do i get it back?

I wanted to update my magellan 4210 gps and it told me to copy the info on the gps onto the computer so i did and than it said to delete the map on it but i accidently deleted everything so now the computer doesn't detect the gps and th gps doesn't even go to the main menu. How do i get the info back onto the gps?