1995 GT cluster problem

Its not my car but i work on it for my stepdad. The mileage on the cluster does not work. I took the cluster out today to see if the cable was loose but found out it didnt have one. The cluster didnt have a place for it. First time that ive seen one like that. Use to the fox body cars. Thinking that the cluster might have something to do with it. The speedometer does work but the mileage or the trip mileage works so any help would be great thanks.