I'm a bit confused on what you are asking but I will answer to the best of my ability.
There is no pre-requisite for becoming an IFBB pro. In other words, you do not have to compete in a natural competition first.
In addition, there are many competitions that are labeled natural. However, the truth is that many of these are not tested or regulated strictly enough. If your choice is to compete naturally, I would do your research and find a reputable natural bodybuilding association.
Good Luck