I agree with Mr. K. The time after you exited on your J-1, counts. It matters not if you have another visa or are trying to come back to the US. You can come in on the F-1 (when approved) and the clock stops when you leave your home country. You are ineligible for permanent residence, immigrant visa, or family based visa eligibilty until you spend an aggreagate two years back in the home country (or you get the HRR waived).