To find #6, you MUST consult a diagram specific to your engine's year and model. This diagram will be in your owner's manual or readily available online via a Ford parts website (like FordParts.com) by entering your VIN or engine details.
Searching online for "[Your Year] Ford [Your Model] 4.6L Spark Plug Diagram" will likely yield the needed image. Looking at the diagram is the ONLY reliable way to determine the location of cylinder #6.