Hi. I dropped my Samsung Galaxy J2 and the screen turned black

When you remove the battery cover look on the back of the phone. There should be a small compartment on the left side just below the camera. Pop the cover off and it will reveal the connector for the LCD screen. Check to make sure the connector is plugged in. To check to see if your screen is the problem, use a friends phone and plug their screen directly into your phone. If their screen lights up and works off of your phone's motherboard then you have a bad screen.