Iphone Music- PLEASE help!!! 4S doesn't work in AUX, but my 3G did???

My first post! I bought a fully loaded 2004 Prius last summer with Navigation and bells and whistles. (I love it - even with 110,000 miles!) At the time I had a 3G Iphone (AT&T) and the bluetooth worked for phoning and the cord that came out of the compartment under the stereo worked for me to plug in my phone and play music. Of course there was no music display and I had to get the music going first and I couldn't view it at all while it was plugged in. (Meaning if I wanted to see the song or change to a new playlist I had to unplug it.) But nonetheless I was STOKED to have my iphone music playing. It also charged my phone.

A few months I upgraded to an Iphone 4S, and now when I plug my phone in I can't play ANY music!! (Bluetooth for phone works fine.)

I've been doing my own research on how to make this happen, but am confused. Can anyone PLEASE help me??? My 3-year old wants to listen to her fave music!!!

Questions:

1. So I always assumed the cord came with the Prius although I guess the first owner could have put it in? Does anyone know if that model came with one?

2. Most importantly: How can I play music from my 4S phone the simplest easiest way for a mama like me who is not very tech savvy....

Mucho gratitude,
Hannah