¿De que país eres?

Another way to say it is "De dónde eres?". Even though you don't say "country" explicitly, people will understand. It's the same in English "Where are you from?" Another would be "En dónde naciste?" o "En que país naciste?" which would be "Where were you born?"

o ¿De qué país vienes?

Se dice: ¿De que país eres?