I borrowed (with permission) a question from Ahmed Han, which is:

People of every religion claim that they are the ones in the right path. Even the people of sects in these religions think that they are on a better path than the peoples of other sects are on. How come could they be so sure?

As a Muslim, how can I be sure that my religion or sect/madhab/path is the rightful one? How can I be sure that there isn't any other religion sent by Allah which is better than Islam, but it is wrongly advertised so that I think that it is wrong?

Change some words and we get:

People of every religion claim that they are the ones in the right path. Even the people of sects in these religions think that they are on a better path than the peoples of other sects are on.

As a someone who believes in Judaism, how can you be sure that the religion is the rightful one? How can I be sure that there isn't any other religion sent by God which is better than Judaism, but it is wrongly advertised so that I think that it is wrong?