multisite: subdomains/subdirectories

I installed once, deleted and installed again a multisite (this is my first installation)

But I am unable to make the sites as subdirectories.

I first install wp with quickinstall, then add to config.php
define( 'WP_ALLOW_MULTISITE', true );
but when I go to tools > Network Setup I don't receive the option to choose subdomains or subdirectories for my installation.

Instead I get a message saying:

"Because your install is not new, the sites in your WordPress network must use sub-domains. The main site in a sub-directory install will need to use a modified permalink structure, potentially breaking existing links."

I stopped here and didn't continue to the installation of "Network Details"

I was following your tutorial in this link:

https://premium.wpmudev.org/blog/ultimate-guide-multisite