How to find a line in files using grep?

Question

linux

How to find all files in the system that have the string str inside, search only among files whose name ends in .conf
Simple grep -l 'str'but searches too long
Tried

grep -l 'str' /*.conf
grep -l 'str' *.conf

But it says No such file or directory

Answer 1

find -name '*.conf' -print0 | xargs -0 grep -l str