Flash to Flex Builder3.0

Hello, currently i am using FlashCS3(ActionScript2.0) and i want to change the entire code to FlexBuilder3.0(ActionScript3.0), the reason why i am asking is, in flash we use to write code in the different frames, but it is not possible in Flex right? and then we use to call gotoFrame(). Then can any one help me in this aspect?