Formal — to staff
Train · Station
すみません、〇〇出口（または〇〇線への乗り換え）に一番近い車両は何両目ですか？ — Excuse me, which car number is closest to the 〇〇 Exit (or the transfer to the 〇〇 Line)? (Train · Station, Formal — to staff, JLPT N3)
You
すみません、〇〇出口（または〇〇線への乗り換え）に一番近い車両は何両目ですか？
すみません、まるまるでぐち（またはまるまるせんへののりかえ）にいちばんちかいしゃりょうはなんりょうめですか？
Excuse me, which car number is closest to the 〇〇 Exit (or the transfer to the 〇〇 Line)?
Romaji: Sumimasen, Marumaru Deguchi (matawa Marumaru-sen e no norikae) ni ichiban chikai sharyō wa nan-ryō-me desu ka? / Reply Romaji: Hai, Marumaru Deguchi deshitara, mae kara san-ryō-me (matawa ushiro kara ni-ryō-me) ga benri desu.
Reply
はい、〇〇出口でしたら、前から3両目（または後ろから2両目）が便利です。
はい、まるまるでぐちでしたら、まえからさんりょうめ（またはうしろからにりょうめ）がべんりです。
Yes, for the 〇〇 Exit, the 3rd car from the front (or 2nd car from the back) would be convenient.
Gesture & etiquette
Show the station map or point in the direction of the expected exit/transfer point.
Do not ask this while the train is arriving or departing, or during peak rush hour when staff are very busy. Have the destination/line ready.