First as you have such a new system you really need to get your system serviced by Apple as its still under warranty!
To answer your direct question:
Both the older four USB-C port models and two port models have three microphones as you can see in the following images.
Here you can see the wholes for the two external mics
The newer two port system has them placed just to the side of the Touch Bar. While not very clear I’ve marked them here
And here is where they are located on the top side of the case
The audio ribbon cable seen here is where they are located on the back side where I’ve marked
Keep in mind only two are used for voice, the third is used to monitor the internal noise to cancel it out.