Your profile's built-in Performance report (Business Profile → Performance) shows it free: searches that surfaced you, profile views, calls tapped, direction requests, website clicks. Trending by month. That's the 'how many found me' answer with zero setup.
Its calls metric counts taps on the call button, not conversations. For truth-grade call tracking, a call-tracking number can be placed as the profile's PRIMARY number with your real number as secondary. Done that specific way, consistency survives; done casually, it scrambles your NAP. Most owners are better served by the built-in counts plus asking callers.
Whichever route: pull the Performance numbers into your monthly five-number review, next to leads and CPL. Maps visibility only matters as far as it produces conversations.