Ive traslated a part of the plugin to hebrew and save

Hi, Ive traslated a part of the plugin to hebrew and save the files wpmu-dev-seo-he_IL.mo and wpmu-dev-seo-he_IL.po on the languages folder - It doesnt seems my WP reading those files - all still in english on my WP hebrew multisite. What exactly should be the filenames needed?