iPhone trade in - how does it work?

Hi,

I’m planning on getting an iPhone 15, when going through the process to check stock on the website there’s an option to trade in my old phone, XS max, for £170ish.

Anyone know how this works exactly? If i turn up to the shop do i get a chance to transfer everything to the new phone and wipe my old phone?

Probably really paranoid but i want to wipe my old phone before letting them have it. I recently read a story about Apple devices making their way to 3rd party refurbishment companies and then on to other customers without being wiped.

 Thanks