You can download a calculator which will tell you your radio security code.
This link gives you the instructions on what to do
http://car-radio-unlock.blogspot.com/2011/05/clio-...
Scroll down a bit and you'll see a blue link called
"Renault Clio Radio code Calculator", click on this and download the calculator.
then using the details you read from the label on your radio, generate the code.

Note. Although the link says "Renault Clio" it does also applyto other models.