* Your vehicle's documentation: The owner's manual will list the fuel tank capacity.
* The fuel tank itself: The capacity might be stamped on the tank itself, though this might be difficult to access.
* The vehicle identification number (VIN): A Ford dealership or parts supplier might be able to look up the specifications based on your VIN.
Without this information, it's impossible to give a definitive answer. Expect it to be somewhere between 25 and 40 gallons, but that's just a broad estimate.
