How to add code for pagenavigate in post?

This has been long long time which i tried to solve, but maybe I didn’t search deep enough. What I’ve tried to have is, let say the post title is “abc happy” and that post i want to have 3 page in it, but when editing its all in one post. In the editor, what code do i need to add in beside the <more>, it didn’t show the page number 1,2,3 in the post.

I want a multipage within the post. I now can have 1,2,3 in first homepage, but can’t have a post which separate to few page. I don’t want to have 3 post like title “abc happy page 1”, “abc happy page 2”. Just want to have “abc happy” and have multipage in it, but when edit, its in one post edit for all 3 page.

Please advice. Thanks in advance.