Based on this paragraph, how many times was Barros traded during his professional basketball career?

The 5' 11" (1.80 m), 165 lb (75 kg) point guard, began his professional career in 1989 when he was selected in the first round of the NBA draft by the Seattle SuperSonics with the 16th pick. Most of his time spent in Seattle was as a backup to point guard Gary Payton, who was considered to be a much more competent ball handler and defender, as Barros was deemed more usable at shooting guard. Prior to the 1993–94 season, the Sonics traded Barros to the Charlotte Hornets in exchange for Kendall Gill. Two days later, Charlotte traded Barros, Sidney Green, and their 1993 draft choice, Greg Graham, to the Philadelphia 76ers for Hersey Hawkins. Barros became a free agent at the end of the 1994-95 NBA season. He signed with his hometown Boston Celtics, and remained for five seasons as a role player alongside David Wesley and Dee Brown and mentor to younger players such as Antoine Walker and Paul Pierce. In the offseason of 2000, Barros was traded to the Dallas Mavericks as part of a four-team deal that also involved the Utah Jazz and Golden State Warriors. By the time the 2000–01 season had commenced, the Mavs had traded Barros to the Detroit Pistons, where he played 89 games over two seasons, averaging 7.5 points per game, until waiving him in 2002.

Based on this paragraph, Barros was traded four times while in the NBA (from Seattle to Charlotte; from Charlotte to Philadelphia; from Boston to Dallas; from Dallas to Detroit).