The Ford Aerostar 4.0L engine is a
V6. Therefore, it doesn't have cylinders numbered 1-6 in a straight line. Instead, they're arranged in a "V" shape. To describe their location accurately requires specifying "bank" (left or right side of the engine) and then cylinder number within that bank. There's no single universally agreed-upon numbering scheme, but a common arrangement is that cylinder 1 is at the front of the left bank, and then they proceed sequentially from front to rear on that bank, then switch to the right bank and continue front to rear.
Unfortunately, without a diagram of the specific engine, I can't provide exact cylinder locations. You'll need to consult a repair manual, a parts diagram (often available online via Ford's website or parts retailers), or a picture of the engine itself to determine the precise location of each cylinder.
