Hi,
When you can hear sound and no image, this is almost always the backlight pannels that are burnt.
Try using a flashlight to see if you can noticed to image in the TV. It will be very very dimmed since there is no more backlight.
If so they would need to be replaced. In some rare cases it may be the power supply board supplying power to the lights, but the vast majority of the time, it’s the lights themselves.
Very common failure in led TV
I hope this helps