In converting, it would be useful to remember this:
These are the abbreviation of the units used in length measurement
*to remember this, you can sing it in Twinkle Twinkle Little Star's tune :)
Referring to the acronym (?) (whatever you want to call it), the distance between km (kilometer) and m (meter) is 2 moves to the right (dam-m). therefore, you must move the number's decimal point 2 places to the right.
Therefore, 257,000 km = 25,700,000 m