When the phone is on and you can hear notifications etc, try shining a torch at an angle close to the screen to check if you can detect any images on the screen at all. They will be very faint if they are there at all, so trying this in a darkened room may help to see them.
If there are images then there is a backlight problem with the screen or perhaps the backlight power supply to the screen on the systemboard.
If there are no images then it is either a screen problem, a screen flex cable connection problem or a systemboard problem.
As a DIY repair for either of the above situations all you can do is to open the phone and check that the screen cable connection to the systemboard is secure and if so, is to then temporarily replace the LCD display to check where the problem may be i.e. display or systemboard.
Here’s the ifixit Samsung Galaxy J3 Emerge Screen Replacement guide, which may help.
Replacement display assemblies are available online. Just search for Samsung J3 Emerge SM-J327P LCD display to get results for suppliers that suit you.