What part of the hemoglobin molecule is eventually metabolized to stercobilin in the feces?

The answer for this question would be: a portion of the heme group

Stercobilin is metabolized from heme of the hemoglobin. Iron from hemoglobin will be recycled and the heme part will turn into bilirubin which will be dump into feses. Inside intestine, bilirubin will be converted into urobilinogen then oxidized into stercobilin