Security Code for Restoring Factory Setting

Hello,

I've been having this problem for months with my Nokia 500 phone.. and it's now saying phone memory full and now I can't even use it to receive important messages or even calls.. and now its phone memory only have 2.6 MB left and I am trying to reset it and it needed security code and I don't know its code.. and I looked at it on my Nokia product and safety information to search for the code and even on its box.. I can't find it.. please help me find or know the security code or how to reset the code to its default security code.. I got some pictures of my phone and its box.. Please help me..Thank you!