need help permalinks!!!!!

when i choose Numeric https://mysite.net/archives/123 on Common settings this is what it says below

If your .htaccess file were writable, we could do this automatically, but it isn’t so these are the mod_rewrite rules you should have in your .htaccess file. Click in the field and press CTRL + a to select all.

<IfModule mod_rewrite.c>
RewriteEngine On
RewriteBase /
RewriteRule ^index\.php$ – [L]
RewriteCond %{REQUEST_FILENAME} !-f
RewriteCond %{REQUEST_FILENAME} !-d
RewriteRule . /index.php [L]
</IfModule>

and Save changes and refresh my site to a certain page it displays this

Not Found

The requested URL /celulas-y-redes was not found on this server.

Additionally, a 404 Not Found error was encountered while trying to use an ErrorDocument to handle the request.