This is an extension for Visual Studio Code, it is an unopinionated XML prettifier. It will only format your XML text, it won't attempt to "improve" or edit the content of the text, only the whitespace.
To prettify an entire documant: Ctrl + Shift + P then type Prettify XML and select dumb-xml-prettifier: Prettify XML.
To prettyfy only part of a document: Highlight the part you want to prettify then Ctrl + Shift + P then type Prettify XML and select dumb-xml-prettifier: Prettify XML.