Jewish ceremonial washing

I am researching the "Water of Lustration" or Water of Purification" and the Jewish baptism of Proselytes/Gentile converts and the Mikve, Tumah and Taharah. I have come here to the WELS so I don't have to get all of my information from the Internet, yet when I put in any of these terms I come up with nothing. This is very frustrating! I would like to know where in the Old Testament it instructs converts to the Jewish religion to be not only circumcised but to have to wash themselves. Also, the specifications to the Mikveh and references to it. Also, the Tumah and Taharah, are they words in the OT?

Your search has been frustrating because there is no instruction in the Old Testament for “converts to the Jewish religion to be not only circumcised but to have to wash themselves.” A ceremonial washing for Gentile converts originated with Jewish tradition and custom. The origin of that ceremonial washing is uncertain. Different rabbinic schools offered their own views on the practice.

Tumah (“unclean”) and Taharah (“clean, pure”) are Hebrew words used in the Old Testament.