Medical schools spend a large portion of the application process evaluating your understanding of the health professions beyond your personal experiences. With that in mind, they look for quality clinical opportunities and first-hand experience with patient care.
There are no set required number of hours for Medical school. The most important aspect is to be able to discuss your experiences in the primary application, through the additional essays in the secondary application, and through anecdotal narratives in the medical school interview.
PA schools and some other health professions do have a set number of requirements. Check the school prerequisite pages directly.
Volunteering and Certifications are some of the best ways to obtain direct clinical care.