Convert from firkin [butter, soap] to milligram

Unit Definition (firkin [butter, soap])
The firkin [butter, soap] is a traditional unit of weight for butter and soap, equal to 4 stone or 56 pounds (about 25.40 kilograms).

Unit Definition (milligram)
The milligram is a very common metric unit of mass equal to 0.001 gram or 1000 micrograms (µg or mcg). One milligram equals approximately 0.015432 grain or 35.274 x 10E-6 ounce.