Lenovo legion y520t-25ikl prebuild cpu cooler upgrade

Hi people. I have a lenovo legion Y520T-25IKL and the cpu is an i7-7700 I want to upgrade the cpu cooler but I am struggling to find one compatible with the stock backplate underneath the motherboard as it is hard to access and I dont have the right screwdriver and it is also alot of effort for me. Anyways I think the screw size I need to use for the mounting hardware is m2.5 x20mm screws (correct me if I am wrong)

So please if someone can help me I would be grateful.