Electrelet Microphone in Amplifier Circuit
Electret microphones need a positive pull up resistor. Forget the pot and 330k and try a 4k7 directly to +9V. The device in the link doesn't have a data sheet but reading between the lines you would probably power it from 5V using a 2k2 resistor and the output would naturally settle to about 2.2V.

Running it from 9V using a 4k7 should be OK but please do measure the voltage on the mic when the 4k7 is connected in case there are any problems.

Background info - Never buy any electrical part that doesn't have a data sheet.