Question

What metric unit would you use to estimate the actual distance between Boston and New York?

Answer 1

The answer to your question is meters.

Answer 2

The metric unit of length and distance is the meter.  Fractional parts
of it are used to describe very short distances, and multiples of it are
used to describe long ones.  For distances by road, the kilometer is
widely used.  That's a distance of 1,000 meters.