If matter can neither be created or destroyed just refined, rearranged, or moved is a true statement and assuming that all newly exalted beings will be creating worlds without end for themselves, then where will we get the materials needed?Are there endless amounts or creating matter and space?
Your question correctly hinges on one little word, “if.” I reiterate what I’ve written in previous answers and some of the articles on this site: we cannot necessarily apply telestial physical laws to celestial elements. We also need to keep in mind that the physical laws that we take for granted may not be the true nature of things. If we use science as it is intended, we accept the theories and laws that we have as the best current working model that describes what we observe, while acknowledging that each has a limited sphere and may still need improvements to match observable phenomena. In short, I do not think we can necessarily assume that conservation of matter as we understand it in our sphere applies equally in celestial spheres.
The Lord has given us some limited insight to His work of creation. In newly revealed scripture, we learn that the site of creation was selected because “there [was] space there,” so they took “these materials” and formed the earth (Abraham 3:24). In a modern revelation, the Lord suggests that there are innumerable such spaces with abundant material for organizing. “[T]here is no space in the which there is no kingdom; and there is no kingdom in which there is no space” (Doctrine and Covenants 88:37).
If you need a visual of how this may play out, you can watch the last scene of “Men in Black” where the concept of multiple nested universes is visually represented.