automatically generated service order from a repair order

hi

I want to create a service order from the repair order (sales order). in the standard system . (in the sales order i select "repairs" for the principal item and if i click back this message is appear automatically generated item proposal and if i press yes for Copy proposal the task list is appear and all iknow how the task list is appear and after that the sevice order is created the question is What's the prerequisites to create a service order from the repair order and how to define this in customizing and why exactly the order type (sm03 ) is the one who will appear

thanks