Hi, I Want To Delay My Period For A Vacation.

Hi, I want to delay my period for a vacation. My Dr. prescribed Norethindrone 0.35mg 1 tablet daily. However, I read online other people said that suppose to take Norethisterone 5mg, 3 times a day, 3 days before expected period in order for it to work. What is the different between Norethindrone vs. Norethisterone? Since my Dr. already prescribed me the Norethindrone 0.35mg, what I should do? Thanks so much for your help.