Simplify the following text for a Grade 6 native English-speaking person.
Original: BÃ thune ( archaic ) is a city in northern France , sub-prefecture of the Pas-de-Calais department .
Simplified: BÃ thune is a commune . It is found in the region Nord-Pas-de-Calais in the Pas-de-Calais department in the north of France .