Two converters, one for the left channel, one for the right.
here is a photo
http://www.maplin.co.uk/images/Full/rw01b&kw36p.jpg
1 stereo cable has 2 connectors, RCA left and right.
Use two adapters to get 1/4" jack plug left and right.
Plug these into MPC left and right inputs.
Job done.
One thing to note is that you should take the ouput from the DJ mixer, not direct from the deck, unless the deck has a line out.
hint: most decks have phono output which is lower in level and also has a tweaked EQ, so will sound funny.