Question

Thieves took away all the money

Answer 1

Question : Thieves took away all the money. (Change into a passive voice)

Answer :

All the money were taken away by the thieves.

Note :

1. In passive voice, the object of the active voice becomes the subject and thus all the money is the subject in the passive sentence.
2. Since the sentence is in Past Indefinite Tense, we use were as the auxiliary verb as all the money is a plural number, instead we use was for singular numbers.
3. The main verb here is took and this is the Past form of take (in Present Tense) which changes into the Past Participle form - taken.
4. As for point 1, the subject thieves of the active voice is now the object in the passive voice and we use by before thieves to determine as it is a subject in its nature.