Getting Live Site Theme Files

I have taken on a client that had a previous WordPress designer build and maintain their website.

One of the elements they need me to get rid of is a part of their paid-for theme. The original designer gave me the original files for the theme that the website, however, I am not sure that if I use the child theme that was included, I would be able to target the right styles.

How do I get access to the current WordPress files for the entire site?