For the purpose of simplicity, since I’m sure you are using HDMI as a video output, HDMI also carries audio. If your HDMI display has an audio output jack, that would be the easiest place to take output from.
If you look at the audio header, one of the pads is SQUARE. That is pin 1.
Unlike an integrated circuit, which counts AROUND the chip (down one row and back the other), headers are counted across. So the one across from pin 1 is pin 2. The next one down the row from pin 1 is pin 3, across from pin 3 is pin 4, etc.
1 – 2
3 – 4
5 – 6
15 – 16
The reason why a header is numbered like this is because they are typically used with a ribbon wire, which interleaves the rows in such a manner that you count the wires in the ribbon starting at 1 on one side, and ending in whatever on the opposite.
So, pins you need are those corresponding to the lines described in the hardware manual page 22 section 7.2. Now I’m not an expert when it comes to dealing with microphones, so I can’t help you any further in figuring out what you need to do with GND_CFILT and MIC_BIAS1. I think, but I’m just learning this myself, that bias applies a constant to the microphone input pin, and that the microphone itself oscillates this against GND_CFILT.