I would write:
1.Sara bought some apples, oranges and grapes from the store.
Because a comma before an and sounds to me like a repetition since 'and' is already something which 'breaks' the sentence
The second sounds fine to me!
Some advice if you don't mind:
1. try to put different titles to your different threads and be more specific instead of being 'general'; i.e. I would have named this thread as 'doubts on commas' ...just to make an example.
2. the right spelling is grammAr, not grammEr
Btw...Welcome to EF and enjoy ![Smile [:)]](/emoticons/emotion-1.gif)