How many people are allowed into heaven according to the Mormons?

Answer 1

Mormons have a criteria for entrance into heaven like most Christian churches to reach salvation or exaltation. Mormons believe that Jesus Christ, through his innate divinity and the Atonement, is solely responsible for the salvation of man.
Salvation is offered to everyone, both living and dead. Anyone who desires salvation may choose to accept it by obeying Christ's commandments.

I think you may be thinking of the Jehovah's Witness who believe that only 144,000 will occupy the Kingdom of Heaven. This is based on a passage in Revelation 7:4, where John describes the tribes who enter into heaven. There will be 12,000 people from each of the 12 tribes of Israel.

"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. Of the tribe of Juda were sealed twelve thousand. Of the tribe of Reuben were sealed twelve thousand. Of the tribe of Gad were sealed twelve thousand. Of the tribe of Aser were sealed twelve thousand. Of the tribe of Nephthalim were sealed twelve thousand. Of the tribe of Manasses were sealed twelve thousand. Of the tribe of Simeon were sealed twelve thousand. Of the tribe of Levi were sealed twelve thousand. Of the tribe of Issachar were sealed twelve thousand. Of the tribe of Zabulon were sealed twelve thousand. Of the tribe of Joseph were sealed twelve thousand. Of the tribe of Benjamin were sealed twelve thousand."

Answer 2

ANYONE who has a good heart and lives by it.

Answer 3

None of the LDS.