Welcome to Android Central forums.
Do you have a Samsung account?
Did you enable Find My Mobile offered through Samsung?
In order to cast your device to an external screen you need to be able to see the screen for the most part. You could mirror the screen via a USB but this usually involves turning on debugging before hand. There are several options available through Samsung's Find My Mobile that might help but the most powerful tools of this service again have to be enabled beforehand which include remote unlock. You can try YouTube and see if there have been any advances or changes that might allow you to gain access on a device without a display but you are very likely hurt on this one.
Good luck though, best wishes.