$v \times \frac{1000 \text{ m}}{1 \text{ km}} \times \frac{1 \text{ hr}}{3600 \text{ s}} \times \frac{1000 \text{ mm}}{1 \text{ m}}$

$v \times \frac{1 \text{ km}}{1000 \text{ m}} \times \frac{3600 \text{ s}}{1 \text{ hr}} \times \frac{1 \text{ m}}{1000 \text{ mm}}$

$v \times \frac{1000 \text{ km}}{1 \text{ m}} \times \frac{1 \text{ s}}{3600 \text{ hr}} \times \frac{1 \text{ mm}}{1000 \text{ m}}$

$v \times \frac{1000 \text{ m}}{1 \text{ km}} \times \frac{1 \text{ hr}}{3600 \text{ s}} \times \frac{1 \text{ m}}{1000 \text{ mm}}$