1. PERFECT PASSIVE

2. 4 principal parts of a verb
ACTIVE FORMS PASSIVE FORMS
present infinitive perfect perfect passive participle
moneo monere monui monitus
I warn to warn I warned I have been warned
Present system stems I have warned
present, imperfect, future I did warn
Perfect system stems
perfect, pluperfect, future perfect

3. How to make perfect passive?
Perfect passive participle + present of verb to be (esse)
Singular: monitus, monita, monitum + sum, es, est
Plural: moniti, monitae, monita sumus , estis, sunt

4. How to make pluperfect passive?
Perfect passive participle + imperfect of verb to be (esse)
Singular: monitus, monita, monitum + eram, eras, erat
Plural: moniti, monitae, monita eramus , eratis, erant

5. Translation
PERFECT simple past completed ACTIVE monui I warned I have warned PASSIVE monitus sum I was warned I have been warned PLUPERFECT ACTIVE monueram I had warned PASSIVE monitus eram I had been warned