What exactly is the "front door" fan? I can understand a front fan but "front door", ... I'm not sure. And, why are are talking about a USB cord? What does that have to do with your fan? If you're looking at a cord marked USB, then you're not looking at your fan cord.
Do you have some documentation for your motherboard which shows various connectors (USB, fans, sound cables, etc.)? You should have such documentation since you just put this system together.