Word Format/Add Numbered Lists to ~40pg Document

A 40pg written document that needs to be put into a numbered list format using Headings/Subheadings to make an automated table of contents. Numbering is 1.1,1.2,1.2.a, 2.1, etc. that is needed. Headers/Footers and format template are already complete. Just need the numbering and alignment done.
It is a small project. (<2-3hrs) However, there are many more documents or templates planned in the future so if this works, we will continue to use the same person and bring them into the project sooner.