LED's generally run at 3.5 to 4.2V, forward voltage. Amperage received to brighten or dim them is usually controlled by a PWM device. To run on aproximately 12 V they are usually run in series, with 3 in series to make up the 12V configuration.
They never run on 12 volts, or 120 volts.
Don't go to Home Depot or electronic stores for advice on RV related stuff like lights. They cater to home owners, not RV or TT owners, who have different electrical needs for boondocking and dry camping.
I'd suggest you save up and buy the portable lamp you want, instead of configuring it yourself, it you don't understand LED lighting and how they work. Or go look in the automotive section of LED lights for one that will plug in to a 12 cigarette lighter type power outlet.
