How to set up a mass redirect from "/" to .html?

Question

PHP

Hello everybody.
Help the pros to solve the situation, preferably with examples if it doesn't make it difficult.
The site is already several years old, I decided to add .html to the pages and posts (WordPress site).
Previously, all pages and posts ended in "/" (about 80 pages and posts)
Please tell me how to mass redirect from old pages with "/" to pages with
.html .html optimization at the end or not. Therefore, I ask you not to prove the opposite, since the meaning of the question is different.
Thanks in advance to people who know for a good answer.

Answer 1

stackoverflow.com/questions/5745490/rewrite-rule-t...
this thread describes how to do it