There is no such thing as converting a license to FAA after private level. You have to meet the minimum requirements of the FAA regulations found in 14 CFAR part 61. All of your current hours will count, but you will have to do the written tests and practical test.
The biggest stumbling block you have is that unless you are a US citizen or have a green card, it is almost impossible for you to do this. I believe you are ineligible for any student visas as you already have a commercial level license.