Convert every rpm within the folder (and any sub-folders, if there are any), with the following command in the terminal:
The above command must be run in the same directory (aka the same folder) as where the files are. So, "cd" to that directory first before running the command. By using the wildcard ("*") you can convert all the rpm into Vector packages in one swoop. Then, after it has created tgz packages from the rpm packages, run the following command on them as root user:
Note, if there's another directory (IE, "desktop-integration", or some other folders), check these to see if they too have rpm files. It's important to install all of them. Generally there's a bulk of rpm files in a directory entitled "RPMS", and sometimes there's a few more in a directory entitled "desktop-integration". It's important to install these as well. The language pack may only have one RPMS folder, whereas an entire LibreOffice package will have a few folders (including a language pack folder) that have both RPMS folders and "desktop-integration" folders. If that's the case, don't overlook the "desktop-integration" rpms.