Where is cylinder 4 on a 2001 Ford Mustang?

On a 2001 Ford Mustang (assuming the 3.8L V6 engine, as it's the most common), cylinder 4 is located on the passenger side (right side) of the engine, towards the rear. It's helpful to remember the firing order to pinpoint it precisely, but the general location is consistent. Looking at the engine from the front, the cylinders are numbered sequentially in the order they fire.