Little help needed from electric nerds amongst us

[BASS-TREBLE]

I'm hoping that someone can help me.

I got one of this cheap little FM transmitters for mp3s in cars that run of 2 AA's.

They have a little plug in the side that I found a spare one lying around for that fits. I thought that I should be able to somehow reduce the voltage from a cars 12V socket to the 3V that the batteries normally provide.
I know that resistors work for the LED circuits but that also has something to do with the current I think, which isn't written on the case.
Can it be done? How?

Thanks
B-T

[HTFU]

You can get a MP3 FM transmitter that plugs into your cigarette socket for less than $10. Would be less hassle.

[Dargor]

what you want is a voltage divider (http://en.wikipedia.org/wiki/Voltage_divider). You probably dont need to warry about the current.