Multiple sitemaps

TSF seems to be creating multiple sitemaps: sitemap.xml and sitemap_index.xml

AHREFS audit is reporting this and they comment “For search engines to crawl and index a page, it needs to be included in a single sitemap. If a page appears in more than one sitemap, it’s not necessarily a problem, but may indicate a bug with the sitemaps setup on your website.”

Looking for advice on this.

The page I need help with: [log in to see the link]