Question

my book has been stolen change it into passive voice

Answer 1

This is already passive voice.
But, if you mean active voice, then it becomes
Somebody has stolen my book.

Answer 2

No passive voice for the given sentence – My book has been stolen.  

The given sentence itself is in passive voice. It has the subject ‘my book’ which is followed by the verbs ‘has been stolen’. The verbs show that it is passive voice and it can be followed by the object ‘by him/her/you/them’.  

So, the given sentence cannot be changed into Passive Voice. As the given sentence is truncated only with the subject and verbs, it may seem to be active voice. But, the verbs show that the sentence is in passive voice.