Log in to old wordpress account

I recently got the task of taking down an old wordpress site that was set up a few years ago.

https://vistainvestments.wordpress.com/

The main https://www.vistainvestments.com has an /index.html redirect to the wordpress site. The problem is that the wordpress site has been crawled and indexed by the search engines and certain information has to come down. My question is since the original developer who made the site is no longer available how can I get this site taken down or given the correct user name and password? Thank you for your help.