The max memory is 8G, there are 2 SODIMM slots that run DDR3 1066, it presently has 4G = 2 x 2G, you'll have to get a matched set of 8G = 2 x 4G, if you decide to upgrade to its maximum capacity.
http://laptops-specs.blogspot.com/2010/11/asus-n53jg-specifications.html
Anytime you get stuck looking for answers try Googling it, that's what the rest have done in this thread trying to help you, cia24 has already provided a link to the memory you actually need if you go through with the upgrade, and additionally WR2 has advised you properly.
So capital_one, at your request, I'm closing this thread! Ryan