JOEL - I believe you are probably talking about Revelation chapter 11, where it talks about two future prophets who will minister in the last days in Jerusalem. After the city of Jerusalem and the temple are rebuilt the Gentiles will begin to try to destroy it again, during which time these two prophets will preach and perform miracles among these people. After about three and a half years the Gentiles will eventually succeed in killing the two prophets and taking over the city. The two prophets will not be burried but will lie in the streets for three and a half days, and will then be brought back to life and ascend into heaven. (See Rev. 11: 3-12)

In our Doctrine and Covenants we learn:
15 Q. What is to be understood by the two witnesses, in the eleventh chapter of Revelation?
A. They are two prophets that are to be raised up to the Jewish nation in the last days, at the time of the restoration, and to prophesy to the Jews after they are gathered and have built the city of Jerusalem in the land of their fathers. (D&C 77:15)

We don't know for certain who these two prophets will be, however an Apostle of our Church Elder Bruce R. McConkie offered his opinion about their identity:

"These two shall be followers of that humble man, Joseph Smith, through whom the Lord of Heaven restored the fulness of his everlasting gospel in this final dispensation of grace. No doubt they will be members of the Council of the Twelve or of the First Presidency of the Church. Their prophetic ministry to rebellious Jewry shall be the same in length as was our Lord's personal ministry among their rebellious forebears." (McConkie, Bruce R. Doctrinal New Testament Commentary. 3 vols. Salt Lake City: Bookcraft, 1965-73)

PATTI - So did Brother McConkie mean that the 2 prophets would be in Israel for 3 years preaching christianity and specifically the mormon religion? would they be born there as Christ was, or do we not know that? do you think they would be the first and only ones to prosilitize there or would there have been others allowed before them, such as missionaries from other denominations?
If it is gentiles who would be the ones to kill them, not jews - are those from Islamic countries surrounding Israel (iran etc) who are most hostile, considered gentiles, as they are non-jews, or is a gentile specifically christian?

JOEL - Anything outside of what the scriptures say is mostly speculation; even what brother McConkie says. The two prophets will probably be preaching the gospel of Jesus Christ (you might call it the Mormon religion) or at least witnessing to all the Jews of His existance and atonement, and because there are two of them, they can stand as witnesses against those who fight against them and eventually kill them (Deut. 17: 6, 2 Cor. 13: 1).
The 3 1/2 years might be more symbolic than an exact amount of time. The three and one-half, or half of seven number (see Rev. 11:9, 11), denotes what is arrested midway in its normal course. The apocalyptic usage of this number goes back to Daniel 7:25. The number is used again after the two prophets are killed and are laid in the street for 3 1/2 days. Among ancient people, such treatment was a means of mocking and generating great shame toward the unburied, their families, and all they stood for.
To a Jew, anyone who is not a Jew is a Gentile. To a Christian, anyone who is not a Jew or a Christian is a Gentile. It depends on your point of view. We don't know who it is that will kill the two prophets; but probably those Gentile troops who will attack Jerusalem.