If your turntable does require an external preamp, then you will need several cables to connect it to your sound system. The preamp should come with the necessary power adapter, so that is taken care of right off the bat.
You will also need two sets of RCA cables. One set will be used to connect your turntable to your preamp, and the other set will be used to connect your preamp to your sound system. This is relatively easy to do, since they are color-coded as red and white. You should also make sure that you get a cable under five feet. Anything longer than this, and you run the risk of the sound being distorted or interrupted.