[NSFW] Migrate my site in WordPress

In a standard web site the web pages are stored in files with the extensions .html, .php, .css, etc. They are all stored in the servers file/folder system.

In WordPress the code is stored in a database. The items that you wish to show on your page are inserted as individual elements which WordPress then stores in the database.
WordPress will allow you to enter plain html code as an element on a page. You have, therefore, two basic choices.
1. Recreate your pages using the available WordPress elements/blocks in the page editor.
2. Paste the html code into a code element in the page editor.