Math Help - convert km to mm

Convert 35 km to millimeters.

On this worksheet, I am supposed to use the prefixes for powers of 10.
I dont understand. How do I set this up using powers of 10?

3.5 x 10^1 = 35km

3.5 x10^7 = 35000000mm

possibly what you are looking for?

Doing it this way is easier to keep up with your units.

35km (1000m/1km) = x

x(1000m/1m) = xx