The S3 uses a micro SIM, whereas all the recent iPhones 5 models use a nano SIM. So strictly speaking, you cannot take the micro SIM in the S3 and put it into an iPhone. You will need to go to Koodo and purchase a nano SIM then activate it on your account. Then you can your iPhone with your telephone number.
The iPhone 4/4S use a micro SIM. In this case, you can simply swap SIM.