Where to store an XML indexing file in a web developement project

I am new in learning web. In our project we have to add an XML file to help browsers to index a website.

I have the XML code to add but I am not where it should be added, is it in a specific folder or just in the root ?

Moreover, which type of XML should I pick ?

<?xml version="1.0" encoding="UTF-8"?>
<urlset xmlns="http://www.sitemaps.org/schemas/sitemap/0.9">
    <url>
        <loc>https://nolark.gil83.fr/</loc>
        <lastmod>2020-09-01</lastmod>
    </url>
    <url>
        <loc>https://nolark.gil83.fr/index.php</loc>
        <lastmod>2020-09-01</lastmod>
    </url>
    <url>
        <loc>https://nolark.gil83.fr/pages/route.php</loc>
        <lastmod>2020-09-01</lastmod>
    </url>
    <url>
        <loc>https://nolark.gil83.fr/pages/cross.php</loc>
        <lastmod>2020-09-01</lastmod>
    </url>
    <url>
        <loc>https://nolark.gil83.fr/pages/piste.php</loc>
        <lastmod>2020-09-01</lastmod>
    </url>
    <url>
        <loc>https://nolark.gil83.fr/pages/enfants.php</loc>
        <lastmod>2020-09-01</lastmod>
    </url>
    <url>
        <loc>https://nolark.gil83.fr/pages/nous-contacter.php</loc>
        <lastmod>2020-09-01</lastmod>
    </url>
    <url>
        <loc>https://nolark.gil83.fr/pages/cgu.php</loc>
        <lastmod>2020-09-01</lastmod>
    </url>
</urlset>