If you have access to the newer version of InDesign (even via a free trial ), use these steps to down-save your file: Open the file in the newer InDesign version. Navigate to File > Export (or use the shortcut on Windows). Select "InDesign Markup (IDML)" from the format dropdown list. Save the file.
To use these converters, simply:
If you own InDesign CS6 or older, and the file was made in CC 2024, you cannot magically convert the file without some access to a newer machine. Here are two free alternatives: how to convert indesign file to older version free