I compiled the source code of LegacyConverter that SDL forum member responded,
and Sdl.Community.XliffToLegacyConverter.sdlplugin was created and I installed according to the wizard.
After that, when I started Trados Studio 2017 (evaluation version), the following message came out.
"SDL Trados Studio detected that you are trying to load an unsigned plug-in.
Sdl.Community.XliffToLegacyConverter.plugin.xml 'has been created by a third party and has not been validated by SDL"
So, I downloaded LegacyConverter from SDL APP Store. Is there a way to register plugins from these files (dll, exe etc.)?