We are not told. You are probably thinking about the 144,000 Jews who will accept Jesus during the Great Tribulation. 12,000 from each tribe. This has been a verse that has been misinterpreted, usually by cults. For example, I had a Jehovah Witness tell me that he was one of the 144,000. He wasn't even of Jewish heritage.
Revelation 7:4 - And I heard the number of them which were sealed: and there were sealed an hundred and forty and four thousand of all the tribes of the children of Israel.
Well...
...he must have been a REALLY old JW, for that number of members was been reached LONG ago, and now new inductees are told that THEY get to stay on a rebuilt Earth; NOT in Heaven!
Too bad, I guess.
(their leadership must have MISSED this verse!)
Revelation 7:9
After this I looked and there before me was a great multitude that no one could count, from every nation, tribe, people and language, standing before the throne and in front of the Lamb. They were wearing white robes and were holding palm branches in their hands.