exhaust pipe questions

I am not sure how to get the guts out of the muffler shell. When i took the cap off i see the threaded bolt going through the "center" but it looks like its been tack welded on there. I cleaned it out with a bunch of penetrating spray but that didnt seem to work as well as I would of liked. Any guidance would be appreciated as i go to put my 1st motor back to use. THANks everyon3. ERICO