If you have prepared the output in HTML, you can convert it to Markdown with converter: https://www.browserling.com/tools/html-to-markdown
Let's see also other examples how to make similar ordered list with HTML/Markdown:
HTML: https://jsfiddle.net/qGCUk/4/
Markdown:
# Rules
1. Rule 1
2. Rule 2
1. Rule 2.1
2. Rule 2.2
3. Rule 3
1. Rule 3.1
2. Rule 3.2
3. Rule 3.3
Also look for tutorial: https://commonmark.org/help/tutorial/10-nestedLists.html
To nest one list within another, indent each item in the sublist by four spaces.