Jesus told Martha that she would see the glory of God -- even though Martha pointed out that Lazarus was dead for 4 days. In other words, Jesus is going to change Martha's perceptions on what Jesus can do.
First off, after removing the stone, Jesus thanked God for hearing Jesus (11:41). Jesus knows that already, but he proclaims it for the people surrounding Jesus so they could believe in Jesus (11:42). Even today, words of prayer can be impactful on the surrounding people. They can know that God cares for them and that there is a way to connect with God.
After prayer, Jesus shouted to tell Lazarus to come out. Lazarus came out -- with bounded head and foot. And Jesus told people to loose him and let him go. In other words, Jesus resurrected Lazarus from the dead -- with Martha (and other people) seeing it in action. Jesus debunked the lie that he can only work with alive people.