# I know a man in Christ

Paul is actually speaking of himself as if he were speaking of someone else, but this should be translated literally if possible.

# whether in the body or out of the body, I do not know

"I do not know if this man was in his physical body or in his spiritual body"

# the third heaven

This refers to the dwelling place of God rather than the sky or outer space (the planets, stars, and the universe).