There's no universal number of friends or weekly visits that defines "enough" — the research points instead to a felt sense of connection, which varies by person.
A better question than "how many"
Ask instead: do I have at least one or two people I could call in a genuine crisis, and do I feel more energized than drained by my current level of contact?
Recalibrate as needed
If the honest answer is no to either, that's the signal to add more structured contact — not a specific headcount to hit.
Introverts and extroverts have genuinely different "enough" baselines — don't measure yourself against someone else's social calendar.