I need to know how old I have to be to choose what parent I want to live with in the state of Ohio

Please pay more attention to posting guidelines. There is a Read First sticky in the Divorce forum (where this was moved from) that directs questions of a legal nature to this forum.

You cannot choose. Also you can do nothing. What has to happen is your mom has to file a petition in Family Court asking for a modification of the custody order. A hearing will be held and you should be given the opportunity to explain to the judge what you want. The judge will then decide based on what the court sees as your best interests.

Unless your mother initiates the modification, nothing will happen.