The reality is that there isn't really a way to CONFIRM the existence of Jesus after 2000 years,
Many people would find this a revelation! They regard Jesus as a real historical figure like the prophets Mohammed or John Smith.
They think Jesus is as real a Julius Caesar or Socrates, but it turns out to be a story that may or may not be based on a real person.
The Jesus we know is from stories written well after his death by people who never met him. How many Christians wrongly think the gospels were written by the apostles? The stories were circulated verbally for decades before being written down in something like their current form.
The oldest books in the new testament are by St Paul (who wrote about half of the letters that are traditionally ascribed to him), who also never met Jesus. He is the main source of the Jesus character, and we have no way of knowing how accurate Paul was, how much of his version is invention. But there are certainly many similarities between Paul's Jesus, and previous figures of legend. At the least, Jesus of Nazareth is a composite character.