Are you asking:

* How many people could fit on Earth? This is a complex question that depends on factors like how densely we're willing to pack people, how much space is needed for resources and infrastructure, and what kind of lifestyle we want to sustain.

* How many of a specific object could fit in Earth? For example, how many cars, houses, or basketballs could fit within the volume of Earth?

Please provide more context so I can give you a useful answer!