Unless you’re an experienced GSM repair technician, take it to a Nokia service center. They have the official flash tool and files for ~$20–30, which is cheaper than replacing the phone.
If you must flash, (e.g., TA-1324, TA-1328) and confirm the flash file contains both system.img and boot.img . Avoid any file that asks for payment before download – most are scams. nokia 6300 4g flash file