Updating Plugin not run

Goodmorning, I have an old version of wordpress that I can’t updat as who has done the web site have changed the css and php of child them. Today I receive this msg on my web site that do not run:

Warning: require_once(/web/htdocs/www.caseificiobusti.it/home/wp-admin/includes/class-wp-list-table.php): failed to open stream: No such file or directory in /web/htdocs/www.caseificiobusti.it/home/wp-content/plugins/wordpress-seo/wp-seo-main.php on line 49 Fatal error: require_once(): Failed opening required ‘/web/htdocs/www.caseificiobusti.it/home/wp-admin/includes/class-wp-list-table.php’ (include_path=’.:/php5.3/lib/php/’) in /web/htdocs/www.caseificiobusti.it/home/wp-content/plugins/wordpress-seo/wp-seo-main.php on line 49

I can’t enter in wordpress too.
How can I solve it? Can you send me an old version of the plug in to replace in the ftp.
Please is very urgent.
Thank you