That depends on the journal you will be submitting your manuscript to. You will need to look at the "for authors" section on the journal website, it should have all the necessary information there. I recommend using something like Endnote which allows you to quickly reformat your references with the click of a button.
If you are submitting to a journal, you should use that journal's citation style. If it's a class for a paper, you should ask your teaching assistant or professor. It would likely be similar to a standard scientific citation style, like one used by the American Chemical Society.