Oh, no... Well, that's not good. Is it possible to do a find and replace? Maybe if the lines you want to number all end with a period and space, you can add a manual line break after each period and space?

For example, under the Find text field, add a period and space (. ) and
under the Replace text field, add a period, space and manual line break (. ^l)

Or maybe find other similarities between lines that you can use for the find and replace? You can hit "Replace" do replace the lines individually or "Replace All" if you don't necessarily want to check each and every replacement.