None of the above.
You are confusing the noun "belief" with the verb "believe". For more information on this, see this related question here. You also are lacking a subject, so that additionally makes none of the choices correct either.
The correct form is
He/she believes in collaborative work.
They believe in collaborative work. (non-gendered singular they)
But this has nothing to do with "collaborative work", so perhaps I'm not understanding your question fully?
Now, I might say:
Her beliefs on collaborative work are irrelevant to this discussion.
In this case, "beliefs" is a noun, not a verb but you need more in the sentence because without it, all you have is a subject.