how to turn raw audio output from analog microphone into mp3 file?

I am working with a RPI Pico w, I have an analog microphone connected correctly and outputting raw audio data, how do I convert it into a file I can listen to?? I am using the micro python language.

here is what I did to solve it:

with open("/sd/audio.wav", "wb") as f:
    print("open")
    for i in range(10000):
        sample = adc.read_u16()
        buffer.append(sample)
        if(len(buffer) == 1000):
            f.write(bytearray(buffer))
            buffer = []
            print("done")
        utime.sleep(0.001 )

you just gotta open it and write to it.

thank you!