How do i find the surface area and volume of the larger figure using that of the smaller figure?

We know that
scale factor=1/8

volume smaller figure=[scale factor]³*volume larger figure
so
volume larger figure=volume smaller figure/[scale factor]³
volume smaller figure=7 km³
volume larger figure=7/[1/8]³> 7/(1/512)---> 7*512---> 3584 km³

the answer Part a) is 
the volume of the larger figure is 3584 km³

surface area smaller figure=[scale factor]²*surface area larger figure
surface area larger figure=surface area smaller figure/[scale factor]²
surface area smaller figure=9 km²
surface area larger figure=9/[1/8]²> 9/(1/64)---> 9*64---> 576 km²

the answer part b) is
the surface area of the larger figure is 576 km²