Check this out:
https://www.laptop-lcd-screen.co.uk/
You can enter your laptop's model in the search box, and will get info about your laptop's display (including backlight type).
They seem to have pages for every laptop ever produced. For example, my laptop's an ACER ASPIRE 5750G 2414G64MNKK, it was produced in 2012, and they have a page for that exact model:
https://www.laptop-lcd-screen.co.uk/shop/ACER-ASPIRE-5750G-2414G64MNKK-15.6-LAPTOP-SCREEN__151325.asp
You can see that it has a LED backlight.