I was studying about a group of order 60, and I found this page; and it says
In the case of a finite nilpotent group (which in this case coincides with finite abelian group), the number of subgroups of a given order is the product of the number of subgroups of order equal to each of its maximal prime power divisors, in the corresponding Sylow subgroup.
but I can't even understand what it means. due to my bad English I guess
could you please explain what it means as simple as possible? and give a proof or hint for this statement?