Could use some help. Wall hung toilet bowl

So here is my issue, an old prison facility built in 1989 with wall mounted ceramic toilets attached to a cinder block wall with fixtures behind the wall located in a pipe chase, the toilets are attached via all thread going threw the wall into the pipe chase, my problem is that they packed a bunch of mortar into the hole the all thread is going threw and as i was removing the mortar to replace the all thread i noticed a small metal plate (probably to keep the all thread from moving around in the predrilled hole) that has serious rust issues, my question is, what is the best way to remove the plate inside the cinder block and the all thread so i can replace it? thanks in advance for any help