Roughly 70% of men your Dad’s age do have prostate cancer, and almost every man has it by his 80s, but that doesn’t mean that treatment is required or beneficial. A biopsy would be a sensible next step: looking at cells under a microscope is the only way to know if cancer is present and, if so, how aggressive it is. I note that you say an MRI can’t be done because of metal in his body; an alternative would be a CAT scan if that’s available where he lives?
Best wishes,
Chris