The answer that you're looking for is Judaism, but actually, the person who leads the prayers in Judaism is not required to be an ordained Rabbi. Rather, they need a working familiarity with the prayers, with any relevant melodies, and with relevant Jewish laws. See also:
Judaism is not a centralized religion with a "head Rabbi" or any single leader. Some countries have chief rabbis, but they are more like advisors for their specific communities. The United States does not have a chief rabbi.
Judaism.
Teacher and clergy person
A rabbi is referred to Judaism. The word rabbi derives from Hebrew and means "My Master". A rabbi can be described as a kind of teacher of the Jewish traditions.
There is no equivalent to a Vicar in the Jewish religion.
You would have to ask a rabbi this question; but generally, a rabbi preaches about the Old Testament and the Jew's religion, and as such they cannot believe in Jesus, as the Apostle John says when he talks about them in John 12.39 & 40
An antonym for the word "rabbi" could be "layperson" or "congregation member," signifying someone who is not a religious leader or clergy member.
Each Jewish community has its Rabbi or Rabbis; there is (today) no central person.
She can convert through a process of study of the religion. The conversion process differs from rabbi to rabbi, and it is currently a topic of much debate in Israel over which conversions are acceptable.
Judaism is not a centralised religion with a single head. Although some countries have a head rabbi for that country, in most places different communities have their own head rabbi. Often, a single city with a large Jewish population will have a different head rabbi for different groups. Israel has two head rabbis, one Ashkenazi and the other Sephardi, for example.
Judaism is not a centralised religion and does not have a person who's the equivalent to the Pope. The title Rabbi means teacher and today Rabbis have a number of roles in Jewish life.
It depends what religion they are. If he is preaching Judaism he is probably a rabbi Catholics are priests and Protestants are ministers.