I have done something similar, my CD’s are all ripped to FLAC and on my Zenith. However my Toyota does not recognize FLAC. I used the DbPowerAmp app on Windows to convert the FLAC files to MP3. DbPowerAmp is not free, but I think there are other apps out there that will do the conversion for you. My vehicle is also limited in the site of the USB stick it will recognize and the formatting used. Do some research on your vehicle and what it will accept.
Listening in car
I recently got a new car with a pretty good audio system and USB input. I want to use a memory stick/flash drive to give me access to many musical options. What's the easiest and least expensive to load music onto a memory stick? I have a Windows PC but, when I go to the music folder, there's not much. I have lots of CDs (now in storage because I now use an Innuous Zenith). Is there a way to transfer the CDs I previously burned onto the Zenith hard disk to a memory stick (I actually tried using a USB drive in my car made from the backup feature on the Zenith but my car would not recognize it). I can load some CDs onto my PC (which does have a disc drive) and then transfer them to the memory stick but it's time consuming and my stored CDs aren't very accessible.