You shouldn't need a pre-amp if it is able to carry signal at all. Just a stereo RCA cable (WITH GROUND) to 1/8" stereo AUX (a.k.a. 2.5mm) for your PC microphone input jack. If you have trouble recording directly into MPC, especially if there is noise (make sure you have a grounding cable installed properly), record into Audacity (then use noise reduction effects to clean up the signal if you need).
The pre-amp is for amplifying the signal for a mixer or directly to a speaker. If the line level is too low for your PC to recognize a signal, then yes a pre-amp (like a mixer or a device like I describe below) will be required.
If you want to go big, you can buy Traktor Scratch Pro or Serato Rane SL4 Scratch Live device with a multi-input midi controller so you can use multiple decks. It comes with its own software (Traktor). These products change all the time so here's the Traktor one I could find that will work for you:
https://www.native-instruments.com/en/p ... h-audio-6/