Is it necessary to wash the clothes, belongings, and utensils of someone who has embraced Islam?

There is no obligation to wash the clothes and furniture of a non-Muslim if he embraces Islam, because the more preponderant opinion is that their impurity is spiritual, not physical. This is inferred from the Prophet's ablution from the vessel of a polytheist woman, the permissibility of marrying women from the People of the Book, and the permissibility of eating their food. Washing is only required if the Muslim is certain that those items have been touched by a real impurity that has not been cleansed.