Pioneer 3000, USB & Rekordbox

At home I use a Numark controller and plug my usb into the usb port and view the music folders I've created on on my Windows laptop to access the music. My USB is Fat32 formatted.

I am DJn this weekend on vinyl, but there's the option to use CDJ3000s, something I've never used before. I've used a Pioneer controller, but I accessed the music through my laptop, so I'm uncertain of how the USBs I use with my Numark controller will interact with the CDJ 3000.

I've been told I can plug the USBs in to the CDJ and access the music in my folders just  like I do with my Numark controller; however, having done some research myself, I'm not sure this is correct. I've read I'd need to use Rekordbox to create my library and then use this to put the music on to my USB. 

My questions are a) can I use my USBs as they currently exists or do I need to use Rekordbox; 2) if I need Rekordbox, does the free version work or would I need to subscribe?

Thanking you kindly in advance.