LUA Capability to tell # of Mobs Near Pet?

I’ve searched but cannot find a way. Seeking if there’s a way to determine how many targets are within Beast Cleave for my hunter pet? Closest I’ve seen is a WeakAura called “Visual Beast Cleave” but haven’t been able to get it to function, nor do I know how it works.

Anyone know if there’s an API that could be leveraged to get the number?