depends on your laptop - what's the make and model? usually has an icon of a display on it - one of the top row of keys; have to press the Fn key simultaneously with it. You may also have a dedicated key.
to check for backlight, get a flashlight, turn computer on, then shine the flashlight at the screen, see if you can make something out. If yes, then your backlight has died and you will need to have it replaced.
also, can you try to connect an external monitor to your laptop and see if external works? if external monitor doesn't work, you might have a motherboard/GPU problem, I'd advise taking it to a repair specialist at that point.
If external monitor works, then the problem is in your laptop monitor, most likely a bad cable or bad inverter. You should take it to the repair shop at this point too, but replacing just the lcd screen of the laptop is a lot cheaper than replacing bad motherboard/gpu.