Other options:
If the data (#ch) is at the end of the text, it can be with this:
=IFERROR(SUBSTITUTE(REPLACE(A1,1,FIND("(",A1),""),"ch)","")+0,"")
Otherwise with this:
=IFERROR(LEFT(SUBSTITUTE(REPLACE(A1,1,FIND("(",A1),""),"ch)",REPT(" ",250)),99)+0,"")