Itunes and Itunes Library on a USB

I drive a car that will not sync with my iPhone 6 Bluetooth. I have tried using a head phone jack from my iPhone to my radio but the signal is weak and the audio isn't loud enough. My question is, "How can I transfer all my songs from my ITunes Library onto my USB flash drive?" My car will play songs off a USB stick but I have been unsuccessful transferring my entire library from ITunes onto 'MY' flash drive. How do I do this? Thank you.

MobileStrike