Converting an existing website to hugo

i have a exciting website with this structure

index.html
about.html
contact.html
Assets/
–CSS
----style.css
–Js
----script.js

how to convert it with hugo with the same styles?
(i want to convert it to hugo because i want to add a blog section for my blogs)

As a general plan—you need to convert the layout (specified in the html) files in Hugo layouts and move the content into some sort of data format (most likely markdown files, but maybe toml/yaml files).

To get started—read the Hugo Documentation on templating and look at the source code of a template that’s similar to what your site currently looks like.

Give it a go and ask for help as you go along.