If you would like to convert meters to kilometers, you can calculate this using the following step:
1 meter = 0.001 kilometers
1900 m = 1900 * 0.001 km = 1.9 km
If the tunnel is about 1900 m = 1.9 km long, then this is a little less than 2 km, because 1.9 km < 2 km.