Paul is actually speaking of himself as if he were speaking of someone else, so this should be translated literally if possible. Paul defends his authority by telling about a wonderful vision of heaven. Although he speaks in the third person in verses 2-5, verse 7 indicates that he was that person experiencing the vision. It was so great a vision that God gave him a physical handicap to keep him humble.
Many scholars believe the "third" heaven is the dwelling place of God. This is because Scripture also uses "heaven" to refer to the sky (the "first" heaven) and the universe (the "second" heaven).