Audio amplifier bridge tied load (BTL) output as analog signal to MCU
If you realy had to use the device you show as an amplifier (although it would not be suitable) you could tap the single + output to feed into a dummy load of say 8 Ohms, and to your analogue input of the MCU, as long as you also connect the - amp ouput to an 8 Ohm dummy load. The problem is that the device you show is not really suitable for microphones. Instead what you're after is more like a microphone amplifier that will provide the required gain you need and possibly other features like AGC etc.
A simple op-amp with suitable gain (say 40 dB) may work very well and its cheap but you may also consider more features than available with simple op-amps, such as with these devices. Other vendors will have similar dedicated analogue gain blocks for microphones all in one package ... Good luck !