Pre-ordered Pixel 8 - Question on required timing of trade in

I preordered a Pixel 8 phone and I am trading in my Pixel 6. Both the pickup of Pixel 8 and trade in drop off are going to be at a local Best Buy. Ideally, I would like to use the Pixel 6 to transfer my existing phone content to the new Pixel 8. Do I have to drop of the trade in when I pickup the new phone or can I bring the trade in back to the store a couple days later after the new phone is properly set up?