Suppose we want to obtain uranium 238 instead of uranium 235 at the end product of diffusion process would we use the same process? If not how we .ca modified it

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To make nuclear fuel from the uranium ore requires first for the uranium to be extracted from the rock in which it is found, then enriched in the uranium-235 isotope, before being made into pellets that are loaded into assemblies of nuclear fuel rods.
Naturally occurring uranium is composed of three major isotopes, uranium-238 (99.2739–99.2752% natural abundance), uranium-235 (0.7198–0.7202%), and uranium-234 (0.0050–0.0059%).
Uranium 238 is not fissionable by thermal neutrons, but it can undergo fission from fast or high energy neutrons. Hence it is not fissile, but it is fissionable. ... For U-235, if it absorbs a thermal neutron, the binding energy released is greater than the critical energy required for fission and so it is fissile.