if you have gained access to this device before your issue and sign in with your Google and Samsung account you could either go to to another device with a browser and and samsung/findmyphone.com or if you have definitely logged in with your Google account and Samsung account you could always just do that factory reset using the button sequence to initiate the hidden set of options which enables you to factory reset the device without gaining access but when re-registering the device from factory settings if you have previously logged in with a Google account or Samsung account you will need the details for that account
