Asalaam o alikum! Who  and when Quran was divided in Thirty paras (juz)? Thanks and regards

Answer

Wa alaikum assalaam wa rahmatu Allahi wa barakatuh.

The answer to your question can be found at this link, insha' Allah: http://www.abouttajweed.com/100202.htm

You are most welcome. Wa assalaam