How do I convert 261 g → kg

Idon’t understand this page, can someone ?

The table describes how some substances were formed substance 19 description formed by boiling pure water formed by combining three hydrogen atoms to every nitrogen atom formed by adding 5 g of sugar to 1 l of water formed by compressing carbon under high pressure based on the given descriptions, which substance is most likely a mixture?

How many molecules are in 6.0 moles of methane