Answer:
I would say that the most critical principle for him/her (the missionary) to understand is the principle or pillars of Islam. By understanding the pillars of Islam, and noting the differences between Islam and the missionary’s religion, it would help the missionary to be able to advertise or proselytize their religion by stating any better alternatives or higher values the missionary’s religion has to offer; this will make it easier to conscientize and convince the Pakistani Muslims to become converts.
It is important to inform the Pakistani Muslims about any higher values that the missionary’s religion has to offer because that can go a long way in having a positive impact on the Muslims conviction, and converting them, or leading them to become converts.