Hi Luca,
to export the content of a database table in an XML format, you can use the "XML Out" component.
In order to retrieve the information, you have to specify an XML Out Entity on the component, by associating the Entity that you want to extract the data.
You can see this article https://my.webratio.com/learn/learningobject/Getting-started-with-Web-Services where is shown a possible usage of the "XML Out" component.
Also, if you want to save the file you can see this topic https://www.webratio.com/forum/question-details/non-riesco-a-fare-funzionare-xml-out-unit?link=ln24d where is explained how to save the final file.
Best regards