3.3v pin on a 5v Pro Micro?
You need to add an external 3.3V voltage regulator. You can get these quite cheap on eBay (etc) as a module - some even come in a breadboard friendly format.

Power it from the 5V from the Arduino, then power your MAX4466. 

However, the MAX4466 can run at up to 5.5V, so I fail to see why you think you need 3.3V.