Connecting SX1 to Car Stereo?

Hi ppl,
I am trying to work out the pins on the usb sync-cable to connect my SX1 to my Car tape deck so I can play mp3's thourgh my car speakers and also get power to the SX1 at the same time.

I have:

1 x SX1 USB cable.
1 x Digital tape with wire to 3.5 male headphone jack.
1 x SX1 car cig charger.
1 x 3.5 famale headphone adapter.

I need to know which 2 pins are used for power
and which 3 pins are used for stereo.

Can anyone help?