I would not use regular expressions as you have constants to replace
So I would use a "normal" replace but a an action group with a chain of them
"vol " -> "Vol. "
"vol" -> "Vol"
" V " -> " 5 "
" IV " -> " 4 "
" III " -> " 3 "
'i_edgars', you have posted into the wrong forum thread.
This pinned thread is for presentation of working examples, not for asking problematic questions.
Nevertheless I will answer. The moderator may split this into a separate thread.