The hebrews'main religious scripture was called the what?

The Tanakh is the Hebrew name for the Hebrew Bible. There are 24 books in all, with the most famous part being the Torah (the Torah is the five books of The Old Testament, shared by Islam & Christianity: Genesis, Exodus, Leviticus, Numbers, and Deuteronomy). The other parts are books of prophets such as Samuel, Jeremiah, and Ezekiel. As well as Psalms and the Hamesh Megillot (Book of Ruth, Book of Esther, etc).

TL; DR: Just say the Tanakh, it has all the essentials of the religion in it, despite the fact many Jews read translations & interpretations of it by rabbis.