I fopgot my formating code nokia 3110c - Nokia 3110 Cellular Phone

Go to settings and reset it, or you can try the defult code 12345. I use this security app to lock my phone.
LEO Privacy Applock Hide Safe Android Apps on Google Play

If you forgot your Nokia Phone's Security Code, you can still reset it by using the Master Security Code of your Nokia Phone. Where to get it? You have to know first your phone's IMEI. To get your phone's IMEI, type *#06# on your mobile. Get the IMEI #. Follow this link. http://www.nokialockcode.com/mastercode.php and type the IMEI of your mobile. Click Generate button and the Master Security code of your mobile will be displayed. Enter the Master Security Code instead of Security code on your mobile when asked to Enter the Security Code.