My phone won't pickup sound, unless speaker phone is enabled.

Try a microphone app. If you don't have any sound being recorded it is the microphone in your daughterboard (the board that has the USB on it). I was able to replace the part in mine fairly cheap. Check the connector as well, if there is damage to it then that might be another solution.

As far as locations, the other two are on the upper end of the phone attached to the motherboard.

Good luck!