A couple’s marriage contract does not need to be renewed if they become Muslim

Ibn Qudaamah (may Allah have mercy on him) said: The marriage
contracts of the disbelievers are valid and may be accepted if they become
Muslim. There is no need to examine the nature of their marriage contract or
how it was done, and it is not essential that their contract should have
fulfilled the conditions of the Muslim marriage contract, namely the wali
(woman’s guardian), witnesses and the format of the proposal and acceptance,
and so on. There is no difference of opinion among the Muslims concerning
that. Ibn ‘Abd al-Barr said: The scholars are unanimously agreed that if a
couple become Muslim together at the same time, they remain together on the
basis of their (original) marriage contract, so long as there are no ties of
blood or via breastfeeding between them. Many people became Muslim at the
time of the Messenger of Allah (blessings and peace of Allah be upon him),
and their wives also became Muslim, and their marriage contracts were
accepted. The Messenger of Allah (blessings and peace of Allah be upon him)
did not ask them about the conditions of their marriage or how they had got
married. This is something that is known via mutawaatir reports and is well
established, thus it is certain.