We have already done the work.

The work has already been done by them

The work has already been do by them

The work has already been done by him

The work has already been done by us

All of the above

Explanation

We have already done the work means ہم پہلے ہی کام کرچکے ہیں

Active Voice: We

Passive Voice: By us

Active sentences in the present perfect tense have the following structure:
Subject + has/have + past participle form of the verb + object
Passive sentences in the present perfect tense have the following structure:
Object of the active sentence + has/have + been + past participle form of the verb + by + subject of the active sentence