Hello everyone ,this may sound dumb but Im new to the remote control world and have recently been on urc control rooms online courses trying to understanding programming urc remotes.So someone gave me a mx-850 but I didnt get a usb cable with it ,I have a serial adapter already ,but when looking at the remote I dont see where the usb plugs in ,all i see is what looks like a headphone jack.Sorry to bother you guys with such a dumb question i just wanna get to practicing with this remote

Yep, it has a proprietary mini-to-DB9 plug. As an end user, I would contact a local dealer and ask for them to order the cord (URC Part# CBL-RS232) from URC.