So you have :0.6g/ml
This is 0.0006kg per ml
or 0.06 kg per 1ml (or 100cm^3)
since 100cm =m
this means you have 0.06kg/m^3
another way of thinking of this is:
(1g/1ml)10 = (1kg/1m^3)
since
1g x 1000 = 1kg
1ml x 1000 = 10m^3
which (when diving top and bottom of LHS)
1g = 1kg
1ml = 10m
so when converting g/ml into kg/M^3 always divide by 10
or 1g/ml = 10g/10ml = 100g/100ml = 1000g/1000ml = 1kg/10m^3
(Remember, case is important M is reserved for Molar, K is reserved for Kelvin)