I suppose that the 4cm refer to the base and the 6 to the height, in that case:
Calculate the area of the base: 4*4=16cm2
Now multiply it by the height: 16*6=96cm3
Since it is a pyramid and not a cube, divide the total volume by 3
96/3=32cm3
The volume of the pyramid it's of 32cm3.
I hope this help you.