What is the prep before immersing in the Mikvah if you had a total hysterotomy and are 65
In your case you would only have to make a hefsek tahara, sine even if you would see blood it wouldn’t be from the uterus. Also when you go to the mikva don’t make the bracha. The reason is because the tevilah is only because of certain doubts, (maybe there was bleeding from the uterus when it was taken out, or maybe not all the places that can cause niddah bleeding were removed).
As a side point, you should have your doctor’s consent before going to the mikva.
NIshmas Avrohom Y”D 188-1, Shevet Halevi 9-178,