The OBD-II port on a 1995 Dodge B2500 van is typically located
under the dashboard, on the driver's side. However, it's not always in the same exact spot, and might be slightly more towards the center or even a little further down than other vehicles.
To find it, look along the lower edge of the dashboard, near the steering column, on the driver's side. It's usually a 16-pin connector. You might need a flashlight to see it clearly.