If you have the complete original car handbook the radio code will be on a credit card sized pice of cardboard in the pack. If not you can get the code off any Renault dealer. You need your logbook to hand to give them the chassis number (this isn't the registration number)....or you can find your chassis number under the car floor carpet to the right of the drivers seat.
Renualt will charge you between �35 - �60 for the code. Alternatively get a perfectly good new cd/radio fitted at an independent car audio shop for about �80. You don't need the code to fit a spanking new stereo.