I'm a little confused about what you are trying to do. If the camera is charged using a USB cable, using any USB charging device will work. More, the camera won't have a 120-240V marking because it isn't being charged directly from a mains supply but at the USB voltage of about 5V.
I am wondering how you are bringing a socket, or is that a reference to the USB socket on a power supply that will be plugged into to a mains supply? It is fairly safe to say these are all going to be dual/multiple voltage devices these days, and should be marked like that.
In all this, the only thing that should have a USB plug is a USB cable. The power supply and your camera should have USB sockets into which a cable is plugged