How many hours — an expression asking about the duration in hours (e.g., "How many hours will it take?").
この映画は何時間ですか？
How many hours long is this movie?
東京から大阪まで新幹線で何時間かかりますか？
How many hours does it take from Tokyo to Osaka by Shinkansen?
旅行中、毎日何時間も歩いた。
During the trip I walked for hours every day.