ALL coaches should have CPR/AED certification, regardless of level.
High School
Most high school coaches also teach which requires a BS/BA for licensure, degree/licensure must match teaching area (Math, History, etc.)
A minor in coaching education or theory may be an option
College/University
Minimum of Bachelors degree, possibly Masters degree if teaching required
Graduate degrees (Masters or even Doctorate) in Coaching Education/Theory may be of interest
Club/Development Sports
Middle School/High School
College University
Semi-Professional/Professional
Certification with a specific organization/sport may be required. These links may be of interest depending on sport interest but be sure to look for certifications for your sport of interest.
https://nfhslearn.com/courses/fundamentals-of-coaching
https://usavolleyball.org/resources-for-coaches/coach-education/