how can we change theme language

Hello Support,

I have faced a strange problem. I have used this plugin and this plugin works fine and it converts all the word-press site into Japanese language. But the problem is that It can’t convert the themes language file into Japanese while we have the .mo and .po file of theme. I have used “Boemia” theme of woo themes. When i have tried to contact to theme’s support. They provides some general steps like these:- http://codex.ww.wp.xz.cn/Installing_WordPress_in_Your_Language

But i know these steps. Please help!

https://ww.wp.xz.cn/plugins/polylang/