Can I send my accepted research paper to IEEE conferences?

My paper in IEEE Transactions journal got accepted one month ago. I wonder if I can modify it a little bit (changing the test case and remove one contribution of the paper out of 3)? If yes, How much does it worth for applying for a phd?

Note: I have 2 papers in Elsevier journal and 1 in IEEE trans. I was thinking to publish something in a conference to show my interest of being amongst others in my field.