Acrobat Pro is included in the Creative Cloud all apps program - both the full price subscription and the student subscription. However, the other subscription will not just "fall away", logical as it might seem. If you just take out a new subscription you will pay for both indefinitely- and there will be a cancellation fee on the old one if it is not prepaid.
Rather than just paying you need to contact Adobe Customer Service. They MIGHT be able to help with this. And they might not, if the student subscription is offered by your school or college.