Lewandowski, who had one year left on his Bayern Munich contract, moved to the LaLiga giants in a deal worth €45million, with a possible €5m in add-ons.
The 33-year-old has now joined up with the Bara squad in the United States.
“I was speaking with Xavi and from the beginning, I know what’s been on his mind, his ideas.
“I’m the guy who wants to play, who wants to win, and I think that with Xavi it’s very possible.
Barcelona will play MLS side Inter Miami CF in Florida, before facing Real Madrid in Las Vegas, Juventus in Dallas, and the New York Red Bulls in New Jersey.