How to set up a redirect for product pages without .html to pages with .html?

Question

htaccess

Tell me how you can make a similar redirect, but ONLY for product pages:
From page:
https://example.com/p375804523-truba-dlya-teplogo
To page:

https://example.com/p375804523-truba-dlya-teplogo.html

Answer 1

Give me a reason why this should be done?
Here I would like an argument for the life of me.
Usually do the exact opposite.