Apostrophe: Possessives, Contractions
Thats my parents car (both parents) / (where does the apostrophe go?)
THAT'S = that is / my PARENTS' car (the car belongs to my parents)
Those are childrens clothes (where does the apostrophe go?)
CHILDREN'S clothes (the clothes belong to the children) / no apostrophe - 'clothes' is a plural noun
Shes 16 years old (where does the apostrophe go?)
SHE'S = she is / no apostrophe - 'years' is a plural noun