Help please!

Google "mercury's surface" age

There you go, all the mercury info you could need;

http://www.nineplanets.org/mercury.html

The relative age of the surfaces of the Terrestrial planets (in which group I include the moon, Io, Gannymede, Callisto and Europa) can be estimated from the density of cratering. Dating of lunar samples has enabled such ages to be accorded absolute numbers. On that basis the surface of Mercury, that we have seen, is around 4 billion years old. We have only seen close up about 50% of the planet. I expect some large surprises when we see the other half.

LOL cratering indeed.

Based on current models of solar system formation,one can say its around 4.5 billion year old.Give or take a few year