How soon after a loss must an insured under a health insurance policy provide notice of claim to the insurer?

My husband had a policy withe Hearthstone Insurance Company of Massachusetts, am wondering how to claim from his policy which I just found in a compartment that I didn't know he had put away. He passed away as of Nov. 9, 1982 of an accident. His Name was Lawrence Pitre, address then Main St. Keegan, Maine 04785. His policy # is 008379258. Please let me know as soon as you can. Thank You. Sandra Pitre