Convert from millimass unit to arroba [Portugal]

Unit Definition (millimass unit)
The millimass unit is a unit of mass equal to 0.001 atomic mass unit, used in physics and chemistry. This unit is also called the millidalton (mDa). The millimass unit is an SI unit, but its proper SI symbol is mu, not the older symbol mmu.

Unit Definition (arroba [Portugal])
The arroba [Portugal] is a traditional unit of weight in Spain and Portugal, equal to 1/4 quintal. However, the Spanish and Portuguese quintals are of different sizes. In Portugal and Brazil, the arroba traditionally equals 32.38 pounds (14.69 kilograms, but in recent years this has been "metrized" to be exactly 15 kilograms). The arroba has also been used as a metric unit equal to exactly 15 kilograms. The name of the unit comes from ar rub', Arabic for "the quarter."