There's no single, publicly available number for the total number of students who transfer *from* UNC-Chapel Hill each year. UNC-Chapel Hill publishes data on transfer *into* the university, but not out. This kind of outgoing transfer data is often considered private student information.
To get an estimate, you would likely need to request data directly from UNC-Chapel Hill's Institutional Research office. Even then, the exact figure might be difficult to obtain due to privacy concerns and the complexity of tracking students who transfer to various institutions.