My mom just baked a cakes.
cake
My mom loves to play with our two puppies.
correct
She ate the whole batch of cookies.
correct
Boil the potatoes and smash them.
correct
I am planning to travel to both country.
countries
Please grab a candies on your way out.
candy
Please put that boxes away.
box
There are many apples in the fridge.
correct
My aunt likes to play with my sister.
Sister and sisters is correct.
I would love to meet both of your parent.
parents
I have to choose between two pair of shoes.
pairs
Mariana and Maru are my friend.
friends
There are only 3 doughnuts left.
correct
Anna left her keys!
Both key and keys are correct.
All of my purse are cool!
purses
Make sure you don't forget your book.
book and books are both correct.