No SMP or post bacc can guarantee you admission to a medical school.
To get an medical school admission, you need to have the good grades (mostly As), especially in your science classes, a MCAT score >510, strong letters of recommendation from your college professors, and the expected pre-med ECs ( community service with the disadvantaged, clinical volunteering, physician shadowing, leadership positions in your activities, and lab bench or clinical research). You also need good writing and oral communication skills, good interpersonal skills, cultural competency, and a whole list of other skills and competencies.
[url=https://www.careercenter.illinois.edu/sites/default/files/Core%20Competencies%20forEntering%20Medical%20Students.pdfAAMC 20 Core Competencies for Entering Medical Students.
To even get accepted to a SMP, you need and GPA>3.2- 3.5 (depending on the program). Formal post-baccs usually require a GPA or 3.0 or above.
Clinical volunteering can be as an EMT, but doesn’t need to be. Clinical volunteering MUST put you in direct contact with patients.