I can't turn on passcode lock on my iphone 5?

Please help. In my iphone 5 settings menu, I tried to turn on passcode lock but it is asking me to type in my old passcode. I had passcode activated once before but I turned it off recently and now I forgot what my passcode was. How can I find out my old passcode?

Hold the home and sleep/on button for 30 seconds at the same time. Then you can go into your settings

You need to go to your phone provider and ask them to help you. There's no way to recover it unless you have a security question or hint.