Do you know many people here tonight?
'Stasera' = sta-SE-ra, stress on second syllable. 'Persone' = per-SO-ne.
Ask this to gauge someone's social connection to the party and potentially offer to introduce them around. It is also a natural way to find out how they are connected to the host, opening many conversation threads.
'Molte' (many) is the feminine plural of 'molto'. 'Qui stasera' (here tonight) anchors the question to the specific event. The phrase 'quante persone conosci?' would be even more specific.
Come conosci i padroni di casa?
How do you know the hosts?
Asking specifically about the host connection
Sei amico/a degli ospiti o del quartiere?
Are you a friend of the guests or the neighbourhood?
Playful way to ask about social circle
Sei qui da solo/a?
Are you here alone?
Can open a conversation about bringing someone to meet them
Italian parties tend to be mixed gatherings where different friend circles meet. The host ('padrone/padrona di casa') plays an active role in introducing guests to each other — this duty is taken seriously. Being introduced through the host carries social legitimacy and makes subsequent conversations much easier.