I presume you realize the two quotes appear to contradict each other.
The first indicates that the true Church will be that founded upon Peter. Presumably any other group of Christians is not included and is therefore a false church. (Discuss amongst yourselves which church is founded upon Peter.)
The second indicates that Christ is there where ANY group gathers in his name. This would therefore include ALL the groups discussed on this thread, including Mormons, JWs, Protestants, Disciples of Christ, Catholics, Orthodox, etc.
“he first indicates that the true Church will be that founded upon Peter”
The statement peter makes is what the Church is founded on not Peter himself.
Jesus replied, “Blessed are you, Simon son of Jonah, for this was not revealed to you by flesh and blood, but by my Father in heaven. 18 And I tell you that you are Peter, and on this rock I will build my church, and the gates of Hades will not overcome it”
LLS
“The first indicates that the true Church will be that founded upon Peter.”
That interpretation is a misreading and achieved by taking one part of the text out of the context of what precedes it, in the whole conversation Jesus is having with the disciples.
The whole begins with:
Matthew 16:13 - And when they came to the region of Caesarea Philippi, He asked his disciples saying, “Who do men say that I the Son of Man am?”
Matthew 16:14 - So they said, “Some say John the Baptist, some Elijah, some Jeremiah or one of the prophets.”
Matthew 16:15 - He said to them, “But who do you say that I am.”
Matthew 16:16 - And Simon Peter answered, “You are the Christ, the Son of the Living God.”
Matthew 16:17 - Jesus answered and said to him, “Blessed are you Simon Bar-Jonah, for flesh and blood has not revealed this to you, but My Father who is in Heaven.”
Matthew 16:18 - “And I say to you that you are Peter, and on this rock I will build my church and the gates of Hades shall not prevail against it.”
In the original Greek it is clear that the text is using a play on words with “the rock” and Peter’s name.
And “the rock” that Jesus is referring to?
It is not Peter, it is Peter’s answer: that Jesus is the Christ.
THAT - Peter’s answer - is “the rock” upon which he will build His church. He blesses Peter for His Father having revealed that answer to Peter.
Jesus then goes on to tell the disciples to not reveal this knowledge - “this rock” of His church (that He is the Christ) to others, for the time for that had not yet come.