“أَمَدَّ” (ʾaamadda)means “He has aided you” in this verse. It is a verb. an action or state word. Here it is perfect verb, verb pattern four, third person — masculine — singular.Corpus grammarV — third person masculine singular perfect verb.
“كُم” (kum)an attached pronoun meaning “you all.” It shows who is being addressed.Corpus grammarPRON — second person masculine plural attached pronoun.