a friend of mine calls me to work on his 4x4 dodge dakota the person before me left the tranny in but stopped work there im trying to figure out where this plug could go im not finding the port on the top or sides of the tranny

 

Looks like the O2 sensor plug.

 

oxygen sensor. its supposed to be on the other side of the trans. when i did my swap i couldn't find it so i cut the wires on the o2 sensor(side) and once the trans was removed it fell down in my face.