Convert OpenXML files
From ArchWiki
The OpenXML documents (docx, pptx, xlsx) are generated by Microsoft Office 2007.
Open Office >=3
As of version 3.0 OpenOffice can read the OpenXML documents.
Open Office 2.4
OpenOffice 2.4 cannot read natively the OpenXML documents but a converter developed by NOVELL is available.
This program called odf-converter
is in AUR.
Install it and run, for a docx file:
$ odf-converter /I <your_file_name>.docx
if the conversion works it will create a file named <your_file_name>.odt
that you can open with OpenOffice.
If it doesn't consider upgrading your OpenOffice version.