Hello I'm Chris

Look on the rotor where the lug studs stick through and see if there are metal assembly clips on there from the factory. If so just twist and break them off with pliers. Next your going to need to break the rust loose. Use a large hammer and strike the rotor about a dozen times between the lugs. If needed use a small piece of wood between the rotor braking surface and your hammer and beat the rotor off from the rear. You will need to twist the rotor while doing this to help walk it off the parking brake shoes inside the rotor.

Thanks for pressing accept, Chris.

That means there rusted BAD. you are going to need to try a 3 jaw puller along with the hammer. I have never had one I can't remove but have had plenty that took alot of effort or the use of a cutting torch (which results in more parts being needed as a result).