Convert from firkin [butter, soap] to pud, pood [Russia]

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 (pud, pood [Russia])
The pud or pood is a traditional unit of weight in Russia. The pud equals 40 funte or 1/30 packen; this is about 16.381 kilograms or 36.11 pounds. The plural is pudi.