Should I retake undergrad classes?

Hi, I’m currently in my first semester of a master’s of science in biology program. Throughout my undergrad career, I was earning As and Bs with about one C a year on an upward trend, with junior year being the worst year due to working and personal issues. In the end, I earned a 3.11 cumulative GPA and 2.9 science GPA, 5 Cs (Chem II, Physics I, Genetics, Biochem, Organic I) and 1 D (Organic II). I calculated that retaking all these classes with an A would bring my cumulative up to 3.25 and my science up to 3.15. I would to apply to osteopathic schools. Would I need to retake all of these classes or just a few, or is doing well in my grad-level science courses sufficient? I.e. taking grad-level medical biochemistry means I won’t need to take biochem again during my post-bacc? If I do need to retake all/some of the 6 classes, should I enroll as a degree-seeking student and just not graduate since undergrad students are given registration priority over post-bacc students?