Rule 7:First make the singular form of the noun into the plural
To use the
possessive form of a plural noun, make the noun plural and
add the apostrophe as with singulars.
boy is changed to boys
man is changed to men
woman is changed to women
Jones is changed to Joneses
Then treat the plural noun as you would any other noun: If
it ends in s, add just the apostrophe; if it does not
end in s, add an apostrophe and an s.
The boys' toys were shared between themselves.
The men's jackets were left in the front room.
We walked through the women's department.
This is the Joneses' car.