彼の部屋に

in/to his room

→ 彼
phrase Uncommon #18,762
in/to his room 彼の means “his,” 部屋 means “room,” and に marks the destination or location. The exact English translation depends on the verb.
JA: 彼の部屋に入ってもいいですか。
EN: May I enter his room?

ずっと彼の部屋に

Have you been in his room this whole time?

— ア・フュー・グッドメン (1992)

彼の部屋に案内して彼にあなたを紹介しましょう

I'll take you to his room and introduce you to him.

彼の部屋には大きなクリスタルがある

There is a large crystal in his room.

被告弁護人相談権利証人は権利を知ってる質問をなぜ彼の部屋に

Why did the witness, who knows about the right to consult with the defendant and their attorney, ask to go to his room?

— ア・フュー・グッドメン (1992)

彼の部屋にほか何も無かった

There was nothing else in his room besides a desk.

彼の部屋にたくさんの本があります

There are many books in his room.

彼の部屋に誰も入れてはなりません

You must not let anyone enter his room.

ボブ彼の部屋にたくさんの本を持っている

Bob has a lot of books in his room.

彼の部屋に家具が多い

There is a lot of furniture in his room.

私は彼の部屋に入ることはありません

I never enter his room.

— TITANE/チタン (2021)