In order to hard reset a Nokia 3110, you should perform the following steps.
Remember! Hard reset will delete all the data on your device; pictures, contacts, messages, apps and more.
Nokia 3110 device will be brought back to the default configuration of a brand new device.
1. Turn on the device.
2. Open Menu, enter Settings and select Restore Factory Settings.
3. Type in the phone's security code (12345 by default).
4. Allow the device to reset and restart. Done.