Quick spanish question!?

Question

the letters are in the post office box.

^if i were to translate that sentence into spanish, what would it look like?

las cartas (son? estan? which word?!) en la casilla..........?

thanks!

Answer 1

estan with an accent mark oner the a

Answer 2

It would look like: Las Letras estan en la caja de la oficina de correos.

Answer 3

Las cartas están en la casilla del correo.

Answer 4

Las cartas ESTAN en la casilla de correos.

The letters ARE in the post office box.

Answer 5

las cartas estan en el apartado correos