If you're looking for a more detailed guide or tutorials on specific conversion methods, here are some additional resources:
How to downsave an InDesign file to open it in an older version how to convert indesign file to older version link
Since your query mentions the word , I need to address package links. If you're looking for a more detailed guide
When asking someone to convert a file for you, do not ask for just the IDML link. Ask for the Packaged Folder . how to convert indesign file to older version link