I can't see what you are asking here. Planets are big things, mostly many thousands of kilometres across, and hundreds of thousands of kilometres from eachother. Millimetres are very small, there are 25 mm in one incch.
Any length or distance can be expressed in mm.
A direct mileage scales is a useful tool that shows distance on a map. This is a scaled down chart that compares the distance on a map with the actual distance.
The distance from surface to surface through the center of a planet would be that planet's "diameter".
The planet Mercury has a diameter of 4879.4 kilometers. Nonsense is the measure of its diameter in mm. But it is 4879400000 millimeters (4.8794 x 109 mm or about 5 billion mm).
109,678 mm
Our planet, Earth.
A planet's maximum distance from the Sun is known as its aphelion. This point occurs when the planet is at the farthest point in its elliptical orbit around the Sun. The distance between the planet and the Sun is greatest at aphelion.
There is something missing from the question. The planet must have a moon. The only way to measure the mass of a planet is by using data about a moon orbiting the planet or data about the path of a spacecraft passing or going into orbit around the planet. If you know the distance to a planet then you can work out the moon's distance from the planet. The planet's mass can then be found. It's a bit of trigonometry and Newton's version of Kepler's Third Law. So that's the reason that it is necessary to know the distance to the planet.
MM stands for millimeter in unit of length and distance and conversion .it stands for millimeters.
By unit of length and distance and conversion ,we can say that 1 cm=10 mm 0.58 cm=5.8 mm
By unit of length and distance and conversion ,we can say that 1 km =1000000 mm its but obvious km >mm
By unit of length and distance and conversion ,we can say that 1 mm =0.1 cm or 1 cm=10 mm