On E3 visa for an Australia Chinese in USA

As a Chinese in Australia with Australia citizenship,MBA degree, I plan to come to USA to find a job, and apply for an E3 visa.

Although I know the principle, but actually in practice what are the jobs that qualify for a E3 visa? Can you give me some detail list? How about a secretary? or manager assistant? or a cell-phone sels person? What kind of employer are qualkified as sponsor for E3 visa?

Can I change from a B2 visa to E3 in USA?

Can you help me to file the E3 visa?

Thank you very much!
yangsun002@zhilan

Victoria