Passive voice form of Model Auxiliaries

You know friends while speaking into English we need sometimes to use model auxiliaries passive voice form.
What is passive voice form let me tell you first the sentences which we use normally while speaking in English they are called A ctive voice sentences you know friends when the verb that is in the sentence effects or acts to the subject  that sentence is called passive voice sentence. Let us see an example.
I can do that.    That can be done ./ That can be done by me.
First sentence is usual means active voice sentence. here verb means the action effects to the object. the action is done by subject
In the second sentence there is no subject means the verb is acting on the object. Really speaking we generally use this kind of passive voice sentences. In other form I have mentioned the subject after by and you can arrange subject if you want.
Let's see model auxiliaries passive form
I Can  do that . That can be done by me.
I should do that. That should be done by me.
I might do that.  That might be done .
I may do that.  That may be done .

I must do that.  That must be done .
I could have helped you. You could have been helped./ By me.
You should have done that. That should have been done .
He might have told him. He might have been told.
He may have told him. He may have been told.
He must have told him. He must have been told.

Friends learn it in easy steps you can watch this video.