create OIS app for my website

i have website already, and i have engaged a OIS app developer, and he had completed the job. But, somehow, i lost his contact and past records. Now, i need modification to my OIS application. You need to do it similar to what i have in OIS application store. My website is Https://koofamilies.com and IOS application is Koo Family. You need to give me source code and guide me to upload to OIS application for replacing the old application. Tell me how long do you need to complete the task.