Ten million meters can also be expressed as 10,000 km, or 10 Mm.
A meter is defined to be the length of the path traveled by light in vacuum during a time interval of 1/299,792,458 of a second. In this way, it can be defined in terms of the second, another base unit of the metric system, and the constant speed of light.
In terms of the number of units, 1,869 is a much larger number, so a student might be confused and say that 1,869 g is more. But since a kilogram is equivalent to 1,000 g, 1.87 kg is actually 1,870 g, which is more. This confusion might disappear once the student is more familiar with the metric system, which makes this type of conversion much easier than converting, say, inches to miles.