Positive pin on microphone
That's an electret microphone.

It has an internal JFET as shown here within the dotted rectangle marked "capsule":



This JFET is needed because the electret capsule is like a small capacitor and only generates very small movements of an electrical charge when sound is present.

That small signal needs to be amplified using a JFET and the external resistor to V+

The positive connection will be the output of the JFET.

To find that connection use a multimeter, one of the two pads will be connected to the case as well and that will be ground, then the other pin will be the positive.

Often you can see the connection between the pad and the case, I think we cannot see it on yours as there is some black stuff covering it. Maybe if you carefully remove that black stuff above the top connection we might see the track to the case. My guess is that the bottom connection is the positive.