The Mormons have a line of succession..and they say they have the keys to the kingdom ..and they agree with you that the scriptures are only correct if they are properly interpreted ..and they are led by a prophet...
How can you prove that you are correct and they are wrong?
History is quite clear. Mormonism is a sect that was founded by Joseph Smith in the 1800s. Besides, they don't even claim to have a successor to Peter as far as I know.