You can use a free online converter to turn your Word.docx file into an EPUB or MOBI file!
Convert Word .docx Using PublishDrive
PublishDrive offers a free, online converter that will accept your .docx file and convert it to .epub and .mobi file in seconds. No login required.
PublishDrive does not require you to create an account, or use their distribution platform. Just upload your .docx file and they will return you an ebook.
If the formatting in your .docx conversion is not satisfactory, you can review their formatting style guide here.