The word 'sixes' means the number 6. It can also mean when you throw a cube and it shows the number 6 on top.
Sixes are usually good because they are a high number and can help you win games.
Examples:
I have sixes fingers on one hand.
In the game, you win if you get three sixes.
He throws the cube and gets two sixes.
I have sixes toes on one foot.
She has sixes dolls in her collection.
The dog has sixes puppies.