Теория:

Пассивные конструкции с модальными глаголами can, could, may, might, must, should, have to образуются по формуле:
модальный глагол \(+\) be \(+\) \(3\)-я форма глагола.
Пример:
they can do it. — It can be done.
They could do it. — It could be done.
They may do it. — It may be done.
They might do it. — It might be done.
They must do it. — It must be done.
They have to do it. — It has to be done.
  
Отрицательная форма пассивных конструкций с модальными глаголами образуется путём постановки частицы not после модального глагола.
Пример:
it can be done. — It cannot be done.
It could be done. — It could not be done.
 
Вопросительная форма пассивных конструкций с модальными глаголами образуется путём постановки модального глагола перед подлежащим.
Пример:
it can be done. — Can it be done?
It must be sent today. — Must it be sent today?
 
Модальный глагол have to образует отрицательную и вопросительную форму при помощи вспомогательного глагола do в нужной форме:
do/does/did \(+\) (not) \(+\) have to \(+\) \(3\)-я форма глагола.
Пример:
it has to be done. — It does not have to be done. — Does it have to be done?
It had to be done yesterday. — It didn’t have to be done yesterday. — Did it have to be done yesterday?