3.5 mm Electret Microphone wiring
Generally, electret mics with a 3.5mm TRS (tip-ring-sleeve) male connectors have a connection like the following:

Tip and Ring are shorted and connected to Mic+.
Sleeve is connected to Mic-.

So if you use the adapters shown, L and R will be Mic+ and GROUND will be Mic- (i.e. GND).
An electret microphone capsule has a FET inside, so there should be a load resistance through a supply to get the sound output:

Image Source: Radioworld.com
Example: PCs provide 3~5VDC through a ~2k resistor. And most 6mm electret mic capsules are happy with 3V through 2k.
Remember that these microphones have an output in milliVolts range, and you may not be able to read the sound output with an MCU. So you'll need an amplifier. There are tons of simple electret mic amplifier schematics on the Internet. The ones with opamps are the simplest. But it's possible to build an amplifier with BJTs/FETs as well.