You have a query object named Items Query.

SaveAsCsv is the correct function to export the query data to a CSV (Comma-Separated Values) file, which is a commonly used text format for data exports.

SaveAsExcel would export to an Excel file, SaveAsWord to a Word document, and SaveAsHtml to an HTML file, but since the requirement is to export to a file and the question doesn't specify any particular file format other than what fits standard data exports, CSV is the most fitting and efficient format for this scenario.

For more information, see the Query Object Functions in Business Central.