If your IDE cable only has two connectors, then yes, you will need to buy a new cable with three connectors. One usually comes with the drive these days, even OEM drives. If not, then the following link will take you to a reseller that has what you need.

http://www.newegg.com/app/ViewProductDesc.asp?description=12-104-113&catalog=1&manufactory=BROWSE&depa=1

You can either buy it from them, or find something equivalent somewhere else since the shipping costs more than the cable, but take a look at the enlarged image so you know what you're looking for.