Our company got an email from google asking us to fix some mobile usability issues with our website. So I logged into the Google Search Console, only to find out that all of the website pages containing mobile usability issues are actually .php code that we definitely did not put on our website. Here's what it looks like, and there are 64 pages of these (and counting).

Image:
https://ibb.co/Y2cftff

What do I do about this? How can I get rid of these?