Head to Home Depot and pick up a braided hose kit for installing the dishwasher. The kit comes with a 48" - 60" braided hose and a 90-degree brass fitting to connect to the water inlet on your dishwasher. The kit should run $11.00 - $14.00.
Edit: 3/8" is the fitting size for the hose itself. The connection to the water input is actually 1/2" or so, but the 90-degree fitting makes the adjustment to 3/8" for you.
Edit #2: Ensure you pick up some teflon tape when you're at the store. Use the teflon tape on the threads for installing the 90-degree fitting to your dishwasher. The braided hose doesn't need any teflon tape on the threads because it has a built-in rubber washer.
MIP - if it's labled 3/8" and looks like it'll fit (i.e. male thread vs. female fitting), then it will work. This is coming from a guy that worked for a few years in a mom&pop hardware store. Best job I've ever had.