Where is the number 5 engine coil on a 2003 expedition 4.6 engine?

The 2003 Ford Expedition 4.6L engine doesn't have a "number 5" coil. The 4.6L uses individual coil packs, one per cylinder. There are eight cylinders, and therefore eight coil packs. They are located directly on top of the spark plugs. To find the specific location for what might be labeled as a #5 cylinder (depending on the engine orientation), you'll need to consult a repair manual or a diagram of the engine. These usually show the firing order and the location of each coil pack relative to the engine.