problem uploading images after moving to new server

I moved my files to a new server and everything looked fine. then I attempted to upload a photo and I get an error message:
Unable to create directory /home/blog/public_html/wordpress/wp-content/uploads/2009/07. Is its parent directory writable by the server?

Initially it appears yo me that the command is attempting to access a folder as it was on the previous server, and this new server has a different location for the files.

In what file is this command line so I can manually change it? Or can I?)

Or is this a different problem requiring a different action on my part?

Thank you