2 km 7 m is equal to

1. 2.7 km

2. 2.07 km

3. 2.007 km

4. 2.0007 km

$2 \text{ km } 7 \text{ m} = 2 \text{ km} + \dfrac{7}{1000} \text{ km} = 2 \text{ km} + 0.007 \text{ km} = 2.007 \text{ km}$

Hence, option 3 is the correct option.