That true church is The Church of Jesus Christ of Latter-Day Saints, also known as the LDS Church or the Mormon Church. I have learned for myself that it is true. Not from physical proof, but from spiritual confirmation have I gained this knowledge. God will let every one that asks know for themselves if this church is true. He gave a promise through a prophet named Moroni in the last few pages of the Book of Mormon that says this:
"Behold, I would exhort you that when ye shall read these things, if it be wisdom in God that ye should read them, that ye would remember how merciful the Lord hath been unto the children of men, from the creation of Adam even down until the time that ye shall receive these things, and ponder it in your hearts.
And when ye shall receive these things, I would exhort you that ye would ask God, the Eternal Father, in the name of Christ, if these things are not true; and if ye shall ask with a sincere heart, with real intent, having faith in Christ, he will manifest the truth of it unto you, by the power of the Holy Ghost.
Another prophet, Nephi, said this about the Book of Mormon:
"And if they are not the words of Christ, judge ye, for Christ will show unto you, with power and great glory, that they are his words, at the last day; and you and I shall stand face to face before his bar; and ye shall know that I have been commanded of him to write these things." (2 Nephi 33;11)