Does adding prefixes to SI units make them no longer SI units?
Yes, when prefixes are used with coherent SI units, the resulting units are still SI units; however, they are no longer coherent.


  The metre per second, symbol m/s, is the coherent SI unit of speed. The kilometre per second, km/s, the centimetre per second, cm/s, and the millimetre per second, mm/s, are also SI units, but they are not coherent SI units.


BIPM: The International System of Units (SI)