Повторить правила образования мн. ч. имен сущ. и образовать мн.ч. по образцу.
a pen- many pens
a box, a child, a men, a family, a boy, a desk, a candy, a toy, a mouse, a bus,
a wolf, a cat, a leaf.

example: a pen - many pens

a box - many boxes

a child - many children

a man - many men

a family - many families

a boy - many boys

a desk - many desks

a candy - many candies

a toy - many toys

a mouse - many mice

a bus - many buses

a wolf - many wolves

a cat - many cats

a leaf - many leaves