Mass, Weight, Density or Specific Gravity of Bulk Materials
Likewise, you will not find a conversion from pounds to metres - the basic units must remain the same - mass converted to mass, length converted to length, et al. You won't usually find a conversion from kilograms to grams - the prefix 'kilo' means '1,000' so a kilogram is in fact 1,000 grams in the same way as a kilometer is 1,000 metres [or about 1,000 yards in 'old money'].