Have a look at the picture below. This is a keyboard from a V5. I do not know if all the variants in the V5 range have backlit keyboards but I assume if you find the symbol as shown on the 'F9' key then yours does.
If present, you toggle the light on and off with <FN> + <F9> keys.
Own a Predator Laptop? Then I bet you have learned a thing or two from beststevie. He has been helping out in this forum for quite a while and it's about time we recognized him for it. Thanks beststevie!