Nowhere!
The concept of conversion emerged within Pharisaic Judaism in the first century and later found its way into today’s rabbinical Judaism. According to the biblical texts, belonging to Israel is primarily defined by lineage (descendant of Abraham, Isaac, and Jacob) rather than by a standardized act of religious conversion. Foreigners (gērîm) who attached themselves to the God of Israel and lived among the Israelites could participate in aspects of Israel’s religious life. However, this desire to attach oneself to the faith does not transform an individual’s ethnicity or genealogical identity. Ruth is a good example. She strongly identified with the God of Israel and the people; however, according to Scripture, she is always referred to as a Moabitess.
Accordingly, in the New Testament period, a non-Israelite who adopted Jewish faith and practice was called a proselyte, not a Jew. Ancestry remained unchanged.
Therefore, in contemporary terms, what is called conversion to Judaism is more accurately described as conversion to rabbinic Judaism, since one cannot convert one’s lineage or ethnic origin.