If someone has a sex change operation from man to woman, can "she" have a baby under hormonal supplementation?

No. It is not possible to restore a functional uterus surgically in a male. Sperm could be cryopreserved prior to a sex-change operation for a male, and then used to produce a pregnancy at a later time in a partner or gestational carrier.
No. They can create a vagina, which is complex but really just a pouch, but not the internal organs of a woman. Hormones can make them look like a woman, but is not magic. They are and would always be sterile.
No. Post-op, she will not have a uterus or ovaries - the surgery changes the outside sex organs, including constructing a vagina, but we can't build internal reproductive organs with current technology. He (pre-op) can freeze sperm for future fertility treatment if desired.