「」。
Naruhodō's law firm is 'one of the world's leading law firms in the energy sector'.
Literal
Naruhodō-sensei [possessive-の] office [subject-が] ''energy field [in-における] world-leading [possessive-の] law-firm'' is.
A reference to the Ace Attorney (逆転裁判) game series — 成歩堂 (Naruhodō) is the Japanese name of the main character Phoenix Wright. The quoted boast is characteristic of the game's extravagant lawyer posturing. ~における ('in X, within the context of X') is a formal/written equivalent of ~での. 世界有数 ('world-leading') is a stock compound — 有数 literally 'having a number' meaning 'ranked among the few.' ~である is the formal declarative copula.