Im a first time mom and I don't have idea.

It's fine to take calcium and folic acid at tje same time. They don't affect each other's absorption in the body. Iron is the one that is not recommended to be taken at the same time with calcium. Most likely your multivitamins contain iron that's why your OB gave you such instructions on how to take your vitamins. You need those vitamins for your baby's development and for your body as well to support your baby's growth.