I'm using the ky-038 mic
Do you have a link to the datasheet or specs for that? (There are a few different "kinds" of microphone boards and the first page of Google hits didn't find the actual specs.)
If you need dB readings you'll need to calibrate with a real SPL meter. Then as long as the "character" of the sound is fairly-constant you can get reasonably-accurate readings. Making a real SPL meter is tricky so if you calibrate your homemade device with "library noise" it probably won't be accurate with a barking dog, etc.
Let's start with this: Are you hooked-up and can you get readings that correlate with loudness? i.e. If you run the code from the [u]Analog Read Serial Example[/u], do you see a difference with loud & quiet sounds?
Take-out the delay, and then I'll warn you that the readings will "look random" because you are measuring a constantly-changing wave (even with constant sound). But once in awhile you'll "catch" a peak of the wave and hopefully you can see a difference with quiet and loud sounds.
Most of these microphone boards have a biased output (so you can read the negative half of the AC audio voltage) so with silence you should read about 512 (half of the 0-1023 range). The louder the sound, the farther up-and-down your readings should "swing" from there.
If you can see "good readings", we can move-on from there.