Trouble with MG811 Pinouts, when off the board.

Recently purchased a MQ811 from DFROBOT and it didnt come with Pin Numbers. Only a Red dot. The data sheet does not help. If anyone have knowledge on this sensor and its pins it would be helpful. I'm aware that the Sensor is also labeled "+MG811" on one side.

I would love to take it off the board and solder it in along with The Arduino Nano onto a  PCB

Thank You