truck it is a 7-way pin I have a four-way pin?

I am trying to direct wire my brake lights to lights and turn signals from the pigtail receptacle on the trailer part of my truck to my tail lights so what I have going on is I have a receptacle and I'm trying to plug in to the factory trailer plug on my truck it is a 7-way pin I have a four-way pin whenever I hook it up I get brake lights turn signals but no running lights where does the running light wire go how do I direct wire this. please help me somebody.