IPS 83689 3.5-Inch Flush Mechanical Cleanout Repair Plug

Remove the threads / pieces completely. (Shove a towel in there first, so that doesn’t fall down the riser). And try one of these. (Or similar) https://a.co/d/0hiLfJ8c Alternative. Just remove the entire metal cap. It’s sitting on PVC. Just throw on a pvc clean out collar / cap on the pvc riser. Easy as it gets. You got this.