"Matti and Liisa, where are you?"
Translation:Matti ja Liisa, missä te olette?
Matti ja Liisa, missä olette? Is correct too. Word "te" can be understood from the - te suffix of "olla" verb. "Te" aka "teitittely" is also really polite way of saying that is not commonly in use modern every day speaking. Good to know of course when you speak to elders, president or work in customer service.