〇〇をする事とっての英訳 教えてください

My suggestions [(2)is the more felicitous]:

(1) 〇〇をする事 [文末] ≈ V(be)[aux] + to be [infinitive] + V(main) [past participle]. Thus:

Unused terminal [device] cables *are to be disconnected* from the power source.

{Literal: Unused cables are to be electrically isolated from the terminal [device].}

(2) 〇〇をする事 [文末] ≈ 命令法. Thus:

*Disconnect* unused device cables from the power source.

My suggestions [(2)is the more felicitous]:

(1) 〇〇をする事 [文末] ≈ V(be)[aux] + to be [infinitive] + V(main) [past participle]. Thus:

Unused terminal [device] cables *are to be disconnected* from the power source.

{Literal: Unused cables are to be electrically isolated from the terminal [device].}

(2) 〇〇をする事 [文末] ≈ 命令法. Thus:

*Disconnect* unused device cables from the power source.