Is this a Unix server? If so, you can write a shell script or, easier, you can create a text file on your local computer that you copy and paste into an ssh window. For example:
mv my-keyword-contact.php my-new-keyword-contact.php
mv my-keyword111-contact.php my-new-keyword111-contact.php
mv my-keyword222-contact.php my-new-keyword222-contact.php
mv my-keyword-faq.php my-new-keyword-faq.php
mv my-keyword333-faq.php my-new-keyword333-faq.php
mv my-keyword444-faq.php my-new-keyword444-faq.php
Because you're writing that list in a text file on your local computer, you can use cut and paste to make things easy.
If it's not a Unix box, you could write a PHP script that changes filenames for you using the rename($old,$new) command.