this is the url of the plugin https://www.emilyrobbins.com/how-to-blog/how-to-configure-wordpress-to-create-search-engine-friendly-urls-for-permalinks-242.htm
and this is the code that i copied to .htaccess
RewriteEngine On
RewriteBase /
RewriteRule ^category/(.*)/(feed|rdf|rss|rss2|atom)/?$ /wp-feed.php?category_name=$1&feed=$2 [QSA]
RewriteRule ^category/?(.*) /index.php?category_name=$1 [QSA]
RewriteRule ^author/(.*)/(feed|rdf|rss|rss2|atom)/?$ /wp-feed.php?author_name=$1&feed=$2 [QSA]
RewriteRule ^author/?(.*) /index.php?author_name=$1 [QSA]
RewriteRule ^([_0-9a-z-]+).htm([0-9]+)?/?$ /index.php?name=$1&page=$2 [QSA]
RewriteRule ^([_0-9a-z-]+).htm/(feed|rdf|rss|rss2|atom)/?$ /wp-feed.php?name=$1&feed=$2 [QSA]
RewriteRule ^([_0-9a-z-]+).htm/trackback/?$ /wp-trackback.php?name=$1 [QSA]
RewriteRule ^feed/?([_0-9a-z-]+)?/?$ /wp-feed.php?feed=$1 [QSA]
RewriteRule ^comments/feed/?([_0-9a-z-]+)?/?$ /wp-feed.php?feed=$1&withcomments=1 [QSA]