How to make all pages on Joomla open by url with /ru prefix?

Question

Joomla

It is necessary that the main page opens at the link https://site_name.ru/ru
And, accordingly, all other pages open like this: https://site_name.ru/ru/page-name
Just on the previous site, all urls were made this way, but now we are transferring it to the new version of Joomla and we want the URLs not to change.
Joomla 3.9

Answer 1

Add multilingual. This is where these prefixes come in.