In order to hard reset a Nokia 3310, you should perform the following steps.
Remember! Hard reset will delete all the data on your device; pictures, contacts, messages, apps and more.
Nokia 3310 device will be brought back to the default configuration of a brand new device.
1. Turn off the device.
2. Open Menu and select Settings and Restore Factory Settings.
3. Tap in the security code (12345 by default).
4. Well done.