If a couple have just enter Islam, do they have to do the Nikah?
Praise be to Allah,
Ibn-Kodama, may Allah blessed him, said that unbelievers marriage is considered lawful when they are converted to Islam and there is no need to check their contract types and how they are undertaken because they do not require a legal guardian, witness, acceptation formula or other conditions of Muslim marriage contract.
Ibn-Abdel Bar said that most Olamas (scholars) agreed unanimously upon the legality of non-Muslim’s marriage contracts in case of thier conversion to Islam together providing that there is no kinships or foster-age between them.
At the age of our prophet Muhammad 
, some people were
converted to Islam together with their wives and he left them on
their marriage and never asked them about their marriage
conditions or how it was undertaken. Finally, this object is
known to us by tradition and necessity so it becomes as an
assured reality