A cable to connect the aux in port (jack) of your soundcard to the record output of your mixer and any freeware line-in recording program.
Simpler: a cable to connect your mixer and your soundcard. Any quality or low quality sound card has an input port for recording music. If you don't have one, buy a card for 15 quid. The cable you will need is a jack to 2xRCA cable. RCA cable ends connect your mixer to your decks. A jack cable end is what you have on your headphones to connect to your mp3 player. Freeware - free. Recording program - any program that records sound on your computer.
Mate, please don't use txt speak here. Full words and sentences are SAFE around here.