Mary- regular shampoo will not get rid of the order. Even if you don't smell it, the cat will.
You need to find one that has enzymes in it that will remove urine odors. There are lots of them, for pets as well as adults. Stores like Petsmart carry many brands and there are also ones online. Zero Odor is one that I've heard works great. I have gotten and used ATX Oder Kill (found online).
Even if you remove the carpet, the smell may still be in the underfloor. Be sure to use a high quality sealer on it and the walls around the area. Those can be found at any good paint store. Seal before you put in any new flooring! Hope this helps!