Kitten
Your co. probably gave you a copy of the codes you will need to know on the test, but in case they didn't, try this
http://www.world-airport-codes.com/
I had to memorize 108 cities before I took my first test. Don't worry about memorizing the easy ones like DEN (Denver), MIA (Miami), LAX (Los Angelas), etc., just concentrate on remembering the harder ones that make no sense, like ORD (Chicago) , MSY (New Orleans), and CVG (Cincinnati). The one I always had trouble with was SDF, for Louisville, til someone told me it stood for Sam Davis Field, then it was easy to remember.
Good luck on your test, and let us know how you did.
P.S. Don't worry about the smartass comments by the pilots, they THINK they're sky gods, but they're not.