How to change sub-bullets from alphabets to numbers in sharepoint?

I am trying to copy a word document to SharePoint site. In the word document, I have used sub-bullets like 1---- 1.1 ---- 1.1.1, 1.1.2 etc. From the above fig, when I paste the content from word to SharePoint, the sub-bullets are automatically in alphabets like a, b etc. Can someone guide me how can I change sub-bullets from alphabets to numbers?