。
Do you have a fountain pen?
Literal
Fountain-pen [object-を] is-holding [question-ますか]?
Possession expressed with 持っている ('is holding' → 'has'), the standard Japanese way to express 'have X' for movable items. (For inherent conditions and body parts, Japanese prefers がある — 熱がある 'have a fever,' 目がきれい 'have pretty eyes'.)