Not the exact data you’re looking for, but hopefully somewhat informative - here’s my post from another thread on COVID-19 infection fatality rate:
From the meta-analysis of IFR from around the world:
(IFR, meaning percentage of infected people who have died)
Under 55 years: “Close to zero”
55-64 years: 0.4%
65-74 years: 1.3%
75-84 years: 4.5%
85+ years: 25%
75% of the 85+ year old group survive. How many of that 75% require medical treatment, I don’t know/haven’t found data on. Also, what’s your definition of “mild?” I’ve learned that a “mild” case of disease in medical terms generally means “not in the ICU,” which isn’t how most people think of the word.