Are you looking to change something like this:
"A"
"B"
"A"
to something like this:
M1 "A" M2
"B"
M1 "A" M2
If so, press Ctrl+H or select "search" and then "Replace..." from the menu bar. Then enter "A" in the Find What field and then M1 "A" M2 in the replace with field and then click on replace all.