Regular expression isn't there to help you in such a situation.
Whatever your HTML tag is will give you finally out put in a browser in a pattern of what you wanted actually, What you want to achieve using Regex.
Dot is a HTML display for unordered li tags.
and number is a HTML display for ordered li tags.
If you want to remove HTML tag and want to attach number in front of text.
then use
THIS[
^] my tip that will remove HTML tags and use that regex to replace with your need in specific pattern.