Conversion factors, 10-2=cm, 10-1=dm, 106=km= 10-6micrometer . Moving the decimal places to the left yields positive exponent, moving to the right yields negative exponent.
63.7mm = 63.7 x10-3 m
= 6.37 x 10-2 m= 6.37cm
=0.637 x10-1 m= .637dm
=6.37x10-5 m (km)= .0000637 km
=6.37 x104 m= 6.37micrometer
63.77 mm is not equal to 637 cm but 6.37 cm or 6.37 x10-2 m. Hope this helps you.
