The 1992 Ford Explorer, with its 4.0L Cologne V6 engine, has a coil-on-plug (COP) system, meaning each spark plug has its own coil. Therefore, there isn't a "coil pack firing order" in the traditional sense like with a distributor.
The firing order itself is 1-5-3-6-2-4. This refers to the order the spark plugs fire. Since it's COP, this is also the order the individual coils fire.