I read there are options for 9" or 10" inch drums, do I remove wheel and measure drum diameter? Or will a 2000 sport have a certain size?

I think the 10" drums have fluting or ridges on the outer surface, which should make it obvious if you have them.

What IJM said.
The 10" are finned.
Also the left and right wheel cylinders are different part numbers on the 10" and the brake lines go in at an angle.
No fins on the drums and brake lines going straight into the wheel cylinders, left and right are the same part number, mean 9".

Or you could just go wild and measure the thing 😜

Yeah I know, take the wheel off.lol.

would this be the same for a 99 XJ rear ?

Yes.