I have read that the Book of Law found in the desecrated Temple by Hilkiah was either the entire Pentateuch or just the Book of Deuteronomy. What has your research and study concluded?

ב"ה Shalom The verse you are quoting actually says in Hebrew "Sefer Hatorah" which literally means the "Torah scroll". In Chronicles II 32:14, this Torah scroll is referred to again with additional information that it was the Torah scroll written by Moses himself. In the oral tradition it is mentioned that when the Torah scroll was found it was opened to the book of Deuteronomy. All the best