What to do during Post-Bacc and for how long?

So I currently a senior with a 3.1 gpa and a 2.8 sgpa. I’m planning on doing a post bacc program but I realized that the program offers 2 semesters worth of classes (3 sciences classes and 1 non science class each semester). Would this be enough to show medical school my growth, assuming I did stellar in the 2 semester?

Also, would I need to do anything else during my post-bacc like volunteering or research or should I just focus on my classes?

Thank you!!