To locate them, look on top of the engine, on the valve covers. They'll be fairly large, rectangular components with multiple ignition coil leads coming out of them. A repair manual or a picture of a 2001 Ford Expedition 4.6L engine will show their precise location. Refer to a diagram in a repair manual to identify which pack serves which cylinders.
You'll need to visually inspect the engine to locate the coil packs. There is no single "G" coil pack.