Did messi wear number 19 for Barcelona?

Yes, he did, from 2005 to 2008.

Messi wore number 30 in his first match for Barcelona in 2004. He then wore number 19 from 2005 to 2008, when Ronaldinho was still on the team wearing number 10. Traditionally, the number 10 jersey on a team is reserved for the best player on the team. Messi then inherited the number 10 jersey in 2008 after Ronaldinho went to AC Milan.