If you cant find that then you can adjust it within your BIOS. When you first turn on the laptop you will get a manufacturer splash screen which will say which key enters the BIOS/setup e.g F2,F10 etc. When in the BIOS you will see brightness go down to that and turn it up full.
As for adjsting it inside windows, if you look at your keyboard one of the keys will have a picture of a sun on it, hold in the Fn key and tap whichever key has the sun on it and that will also brighten the screen.
Christy