http://www.google.com/search?q=HEMI+combustion+chamber&hl=en&prmd=imvns&bav=on.2,or.r_gc.r_pw.,cf.osb&biw=1680&bih=949&um=1&ie=UTF-8&tbm=isch&source=og&sa=N&tab=wi#um=1&hl=en&tbm=isch&sa=1&q=spark+plug+chart&pbx=1&oq=spark+plug+chart&aq=f&aqi=g1g-m2g-S6g-mS1&aql=&gs_sm=s&gs_upl=10762l20623l0l23258l16l16l0l2l2l0l194l1877l3.11l14l0&bav=on.2,or.r_gc.r_pw.,cf.osb&fp=8cd9febe539bdb93&biw=1680&bih=949
Here’s some photos of faulty spark plugs to show you “what you’re looking for”. I still suggest you remove a couple of plugs from the functioning cylinders. That way you’ll learn what good plugs look like compared to “bad” ones. The photos usually show extreme conditions, so it’s helpfull to look at real plugs from from your engine.
As your HEMI has two plugs per cylinder, you will be able to compare the two against each other and if they look the same, you can compare them to plugs from an adjacent cylinder that that is known to be firing.
If they are simply not firing, you’ll see carbon fouling. If one is fouled and the other is OK the fault may be with the plug. If they’re both fouled, the fault is probably in the circuit and you’ll need to check the coil pack that fires them next.
If both are getting current from the coil pack and they’re carbon fouled, suspect the fuel injector as Eric suggests.
Eric’s suggestion to perform a balance test (disabling current to each cylinder, one a time, to find the the bad cylinder) is a good idea because the fellow at the parts store that scanned and read the code and told you it was number 3 cylinder, could easily be wrong.