USB C to USB A pinout
It's the D+ and D- like normal. There is two of each because USB C is supposed reversible. You can insert the plug both ways and it will still be a valid USB 2 connection, as usb 2.0 does not negotiate the pinning. Flip the plug 180 degrees and the same pins will connect in the same order. Your board should connect both together for maximum connectivity. 

There is no ID pin, as that's only implemented on plugs. In USB C, the CC pins handle this, and pulling them to ground with a 5K resistor will initiate OTG HOST mode on the other side of the link.