Doctor's. Like to know with ovarian cancer stage 3. If doctor tells you after treatment you are good will they give you chemotherapy for precaution?

Most likely. Assuming the statement was from the surgeon he/she most likely meant that they successfully removed the majority, if not all the cancer they could see. Research has shown that chemotherapy administration after surgery for stage 3 disease is beneficial; therefore, you will most likely be offered the treatment. The treatment is to reduce the risk of recurrence and can be viewed as precautionary.
Surgery/chemotherapy. The standard of care for stage 3 ovarian cancer is both surgery and chemotherapy. Surgery is often performed first to debulk the cancer. Since it is difficult to remove all cancer by surgery alone, patients often undergo chemotherapy after surgery.