Here are some general guidelines to follow:

• Use an apostrophe and “s” to indicate possession with singular nouns. For example, “The cat’s meow” or “The car’s engine.”
• Use an apostrophe after the “s” to indicate possession with plural nouns that end in “s.” ...

Apostrophe Placement Rules

• For singular nouns, the apostrophe is placed before the “s.” For example, “the boy’s toy.”
• For plural nouns that do not end in “s”, the apostrophe is placed before the “s.” For example, “the children’s toys.”