Since you purchased from Best Buy, you will have to consult with them.
Here is the process I followed to get my serial numbers for an Elements 13 bundle purchased at Best Buy a few months back, starting with the getserial URL in Step 1:
You can only redeem the redemption code once to get the serial number so make sure you write down the serial number, print it, and/or copy/paste into a document for later reference.
Not true that only Best Buy can help you. Also the link somebody else provided is useless because those are the instructions I followed and it just kept telling me I did not need a serial number. I reached out to the help desk via chat and they were excellent. All you have to do is login to your Adobe account (it made me create one during installation) and click on your name at top of screen. Select Manage Account, Plans and Products, View your Products and you will find your serial number. Easy, once you know it is there, and it should always be there.