The 6pin header connections are the same as the pinout on the USB serial light adapter linked above. On the Arduino side, the pins are like this. Pin 1 is the pin 1 is the closest to the regular TX / RX pins and the pin 6 is next to the micro SD reader.1. GND2. Not connected3. 5V4. RX5. TX6. ResetThese signals are from the perspective of the Arduino, so RX lets the Arduino receive data from the computer, while TX lets the Arduino send data to the computer (it depends on how your serial adapter is labeled if you need to connect RX-RX and TX-TX or if you need to cross them. You might just need to try both).The reset pin allows automatic reset and is commonly connected to the DTR pin of your serial port to auto reset when the serial port is opened (but you can also use manual reset, where you press the reset button and then quickly start the upload process within the first second or so after releasing the reset button).
The connector does not seem to be marked!