We should start from figuring if it’s indeed a screen issue. First try with shining a torchlight to the screen via the Apple logo in the lid, if you see a dimmed out image it’s a backlight problem. If you have no image at all try plugging your Mac to an external source through an adapter, a TV or ext. monitor would do. If you have no image it’s not a screen problem, but a logic board fault that is quite common on your Mac model.