To find the firing order, check:
* The engine block: The firing order is sometimes stamped directly onto the engine block itself.
* The owner's manual: This is the best source for this information.
* A reliable online resource: Websites like Ford's official site (if they have that info archived), or dedicated automotive repair sites, may have the information if you provide the engine type and displacement (e.g., 4.6L V8, 5.4L V8, 7.3L Diesel).
Provide the engine details, and I might be able to help you find the firing order.