As far as we know, no easy way how to directly convert .iwa files (iWorks documents) to anything else exists. Such .iwa files are typically found inside compressed documents from iWorks (.pages, .numbers etc.) and replaced the previously used XMLs that were utilized for the document structure. In case that you want to convert your .iwa document to MS Word format (.doc, .docx), which is what iwa to docx conversion essentially represents, you will need to convert it as whole, not just a part from inside.
It actually might be possible to somehow decode the IWA format (they feature Snappy compression) and rebuild some kind of "old" version of iWorks documents, but that seems like highly unreliably and complicated way.Open IWA file Open DOCX file
Mobile version of popular word processor from Apple
A word processor and layout tool marketed by Apple