https://www.youtube.com/watch?v=kA_pbMR6jVs
I watched this tutorial and could not help but be disturbed by the fact that this man hooked up servos to a 9v battery... and how many mA can these batteries even supply? the one i have has the capacity of 400 mA's
You really mean mA, and not mAh?
And no, a 9 V battery isn't well suited for even medium load.
honestly i didn't even know the difference between mA and mAh
It's easy to mix them up, but that little h make a big difference. Usually you only see how many mAh a small battery is capable of, but like car batteries have both A and Ah specified.
Fortunately, you recognized that the video is complete nonsense, which is pretty common for technical subjects. Beware!
mA = milliAmperes = measure of current flow
mAh = milliAmpere hours = measure of battery capacity (amount of energy stored)
1 mAh = 3.6 coulomb
1A = 1 Coulomb / second = 6.2415 x 10^18 electrons / second
Tom.... 
Why were you disturbed?
What is wrong with using a 9V battery?
Use the forum search to look up all posts that mention the terms "9v battery motor", and you'll find out why someone might be concerned...
Most mention fire alarms/ smoke detectors and seem to be totally irrelevant at solving the OP problem.
Because i thought using a higher volt battery could potentially damage something that usually runs on 5 volts? Plus all the comments were completely oblivious to it too...
That is absolutely true but you seemed to be more concerned about the 9V mAh rating and not the voltage.
i am new to this and accidentally mixed up mAh with amps and was wondering if a 9v battery that had the mAh of around 400 or 550 could power two of something that required the current of 250-360 amps. just a misunderstanding on my part
Again you are confusing things.
The mAh rating specifies how many milliamps the battery can supply for one hour. It does NOT specify the maximum current it can provide. A good Alkaline 9V could supply up to 1A of current but only for a short period of time
I assume you mean 250-360 milliamps (mA) and a 9V can certainly provide that much current but of course you have the problem of supplying 9V to a 5V device.
Supplying servo with higher voltage causes servo to draw more current. Having low discharge current battery probably saved your servo. 9V "box battery" might be ok for YT videos, but not in real life.