I am using Windows 8.1 and am running Libre Office 4.2.0.4. Are there extensions, plugins and the like available. I am representing a church group which has documents in these old formats.
This answer indicates LO v4.x no long supports opening of the old binary Star Office v1.x-v5.x file formats. To obtain the required filters in a v3.x install it is necessary to ensure the Legacy Filters are installed (chose Custom installation).
LibreOffice 4.2 does not have the filters at all. It is not optional in 4.2 but totally removed. You need a version 3. I would look for a portable version, keep it together with the documents, and convert the documents with the wizard, which is integrated in version 3.
@Regina, thanks for the correction. I will modify my answer accordingly. My brain is not functioning this week.