It doesn't seem like a direct gdoc to docx conversion is possible, nevertheless you can access the link to download the document and further export it to one of the available formats. When you open your .gdoc link files with Google Drive, you can access and download the file as MS Word document, simply with the File ► Download as function in the upper menu.
However, this requires that you are on-line and also have access to the Google account on which the documents are saved and located. Unfortunately, you cannot just take any random .gdoc file and convert it as .docx file, because .gdoc files are just links to the documents and do not contain the documents itself.Open GDOC file Open DOCX file
Word processor web app from Google