The plural possessive form of "strangers" is "strangers'." For example, "The strangers' cars were parked outside."

Company of Strangers - Company of Strangers album - was created in 1992.

A full of strangers

There is no specific collective noun for strangers, in which case a noun suitable for the situation is used, for example a family of strangers, a neighborhood of strangers, a congregation of strangers, etc.

The word "strangers'" is plural possessive, indicating something that belongs to multiple strangers.