i am gonna buy some colder spark plugs perferable 2 steps colder (ngk's) and i dont know how to tell if they are colder and dont want the guy at like auto zone to give me the wrong ones so i did some research and found this number ngk BKR7E

if anybody could tell me if these are two steps colder or which ones i need that would be great.

stockers=ZFR4F-11


now that i think about it would it be ZFR4F-9 or would it be ZFR4F-13