Now do these exercises:
http://www.agendaweb.org/exercises/verbs/passive-write-2
https://www.ego4u.com/en/cram-up/grammar/passive/exercises?02
http://www.learnenglishfeelgood.com/esl-passive-voice-exercise1.html
http://eslus.com/LESSONS/GRAMMAR/PASSIVE/Gramc.htm