If your "unlock" request is actually about a forgotten (rather than a SIM lock), you can perform a hard reset: Nokia 3310 User Guide: Restore factory settings - HMD
Insert a non-accepted SIM card (e.g., a different carrier’s SIM). Your phone will prompt: "Enter restriction code". Type the NCK code generated. Press "OK". The phone will reboot and display "Unlock successful". If your "unlock" request is actually about a
Tools such as the doctorSIM Nokia USB Reader can be used to read the phone's hash via a USB cable, which is then used to generate the final unlock code. 3. Factory Reset (Screen Lock Only) If your "unlock" request is actually about a