Hello,
You need to configure the conversion plugin to use it.
If you get an "Undefined array key path" error is because you are using the conversion plugin based on LibreOffice and you have not set the path to LibreOffice in the config/phpdocxconfig.ini file. On https://www.phpdocx.com/documentation/conversion-plugin/conversion-plugin-installation-and-set-up you can read how to configure it.
On https://www.phpdocx.com/documentation/conversion-plugin you can read all the information about how to configure, debug, and use the conversion plugin. In the package, you can also find samples using all conversion plugins (examples/FormatConversion/transformDocument folder).
Regards.