What is the correct passive voice of the sentence :You must help me?

I must be helped by you.

Me must be helped by you.

I must helped by you.

I must have helped by you.

Use the correct form of the verb "be" according to the modal ("must be").

Use the past participle of the main verb ("help" → "helped").

Add the agent (the doer of the action) at the end if needed ("by you").

So,

Active: You must help me.

Passive: I must be helped by you