To create an XML Sitemap, you will first create a Standard Sitemap Protocol Feed as explained here.
After that, from the Feeds tab of the Marketing page, select the XML sitemap feed you wish to create, and click Process Now.
There are two methods to view an XML sitemap.
Click the Marketing header on the left side of the page, then click the Feeds tab.
Click on a feed to edit. In the Edit Feed box that opens, click View Sitemap.
Open a browser, and navigate to your XML sitemap page.
For example: If your store domain is “mivatest.com,” and your XML sitemap file name is “sitemap.xml” (the default sitemap filename without a suffix), then you would navigate to https://mivatest.com/sitemap.xml.
Click the Marketing header on the left side of the page, then click the Feeds tab.
Click on a feed to edit. In the Edit Feed box that opens, click View Sitemap.
The XML sitemap will open in a browser window. Then click the File menu, and then Save.