no pressure shower/tub

We recently bleached our hot water heater. When all faucets were turned back on, several were clogged with sediment/gravel. I have been able to clear all except my daughter's bathtub/shower. I have the handle and trim off and now am stuck. Am I looking for an aerator, a cartrige or what? And what do I do once I find it!? I have spent sooo many hours on line! It is a moen single handle with posi temp. I believe model T3111 (or similar). Any advice would be much appreciated!!

Had the same thing happond a few weeks ago from a under the slab busted main water line and I think I had installed a Moen shower value too. After the trim came off had to take out 4 screws to pull off a brass plate holding in the cartridge. Of course turn off the water first. I pulled out the cartridge and took out the 4 screws and nut on the sides to get to the back to find two small spring loaded filters that had clogged up with sand. Gently flush out with water. I had installed new shut off values to the new bath so I was able to turn off the water to the bath and still have water on the house. It took a couple times to get all sand out of the system but finely was able to clear them. Be easy on the little spring filters.