Здесь нужно просто сделать отрицания. В первом случае - несокращенное, во втором - сокращенное.
They are not chairs. They're not chairs.
We are not English. We're not English.
She is not ten years old. She's not ten years old.
It is not an orange. It's not an orange.
You are not from London. You're not from London.