In one mol of any molecular compound there are Avogadro number of molecules. Avogadro number is 6.022 x 10^23 molecules.
So in 1 mol of any mol of a molecular compound the number of molecules is 6.022x10^23 molecules.
In 4 mol of compound it would be 4 x 6.022 x 10^23
The answer comes out to be 24.088 x 10^23