There must be at least three adult males present, in addition to the imām (leader). If there are not enough people, the group will pray Zuhr prayer instead. Friday [Jum’ah] Prayer can be prayed in any mosque, building, or even in an open area.
Reason for Asking the Question
Some people find it very difficult to make it to a mosque due to class, work, or some other reason. They know that this prayer is a requirement for adult Muslim males. By knowing the minimum number, they can fulfill the requirement by gathering a few Muslims nearby and hold their own Friday [Jum’ah] Prayer.
Shaykh Mustafa Umar