On a standard guitar amp, there are three EQs lows, mids, and highs. I know the lows affect the low frequencies, the mids affect the middle frequencies and the highs effect the high frequency. What I would like to know in general, what notes on a guitar do each of the three EQs represent?
I think there potentially a misunderstanding here: Let's say you play an A3 (7th fret on the D string or 2nd fret on the G string). The pitch is A and the fundamental frequency is 220 Hz. However there are also many so-called harmonics, which are multiples of the fundamental. So you get 220Hz, 440Hz, 660Hz, 880Hz, 1100Hz, etc. In fact, majority of the energy is in the harmonics. That's the main reason why different guitars sound differently. The relative ratio of the harmonics are different.
The EQ mainly impacts the balance of the harmonics. While the treble control only impacts frequencies above, say, 1 kHz, it still has a lot of impact on our A3 note that has a fundamental pitch frequency of 220 Hz.
Cross referencing with this pitch/frequency guide http://www.phy.mtu.edu/~suits/notefreqs.html
This is going to be different for every amp though. So you could use the documentation for you amp and check the pitch frequency table listed above to find out the pitch range for the knobs on your paticular amp.