This can be stated in active form. AT: "let people and animals wear sackcloth" or "let people cover themselves and their animals with sackcloth" (See: [[rc://en/ta/man/translate/figs-activepassive]])
"pray earnestly to God." What they were to pray for can be made explicit. AT: "cry out loudly to God and ask for mercy" (See: [[rc://en/ta/man/translate/figs-explicit]])
The king used this rhetorical question to get the people to think about something that they might not have thought possible, that if they would stop sinning, God might not kill them. It could be translated as a statement: "We do not know." Or it could be stated as a word and be part of the next sentence: "Perhaps." (See: [[rc://en/ta/man/translate/figs-rquestion]])