So, I’ve been considering transferring to Duke, but I don’t know if it’s possible to transfer to become a junior instead of a sophomore (if I have enough AP credits from high school).
If you are accepted for admission, Duke will give you a preliminary estimate of how your credits will transfer. You probably won’t know the final status of your transferable credits until after classes have started. If you want a pre-evaluation of the AP credits plus the coursework you are taking now, discuss that with the transfer admission team at Duke.
How Duke evaluates AP scores should be easy to look up on Duke’s web site.
Transfer credit and equivalency for college courses may have to wait until after you matriculate if you are admitted.
Duke’s transfer credit policies are listed at https://registrar.duke.edu/student-records-resources/transfer-credit .
You also need to look at how any AP and other credits meet the degree program in which you are enrolling. Having dozens and dozens of GenEd credits won’t help you get through an Engineering program, as an example, any faster. You may technically be a Junior, but will have 3 years of courses that need to be taken to graduate.