* Check the Vehicle Identification Plate (VIN plate): This plate, usually located on the driver's side dashboard, will list the engine code. You can then cross-reference that code with a Ford engine code decoder (easily found online).
* Look at the engine itself: The engine block will have a casting number which can be used to identify the engine size.
* Check your owner's manual: If you still have the original owner's manual, it will specify the engine size.
Without additional information beyond the 8th VIN character, it's impossible to determine the engine size.