The Oxford comma is a hotly-debated, free and easy punctuation mark – as explained in this video from TED-Ed.

Its use is basically optional; you can add it or not, as you see fit, as long as you are consistent within a single text.

I have always had a lot of respect for this punctuation mark and its continued existence, against all the odds. Attention to this sort of detail is something you might want to look for in a translator.