As far as we know, there doesn't seem to exist a way how iWorks .iwa files could be converted to anything else and particular not to PowerPoint Presentations (.ppt) through iwa to ppt conversion, you have to look for key to ppt conversion.
In most cases .iwa files are found inside compressed documents from iWorks (.pages, .numbers etc.) and these replaced the previously used XMLs that were utilized for the document structure. If you want to convert your document, you will need to convert it as whole, not just a part from inside the archive.
It also might be possible to somehow decode .iwa files (they feature Snappy compression) and rebuild some kind of "old" version of iWorks documents, but that seems like highly unreliably and complicated way to achieve things.Open IWA file Open PPT file
Presentation software for iOS operating system, developed by Apple
The most popular presentation software for Mac