I wouldn't make any sudden changes at this stage, ask them what they are using and keep him on that for now, make any changes as and when you have to or want to in a few weeks time, I would say, depending on what you think would be the best feed.
Mine was on Hill Science Plan puppy food when I got him. I had already bought James Wellbeloved (I had wanted Burns but couldn't source it locally) to slowly move him over to. However, he wouldn't eat any of the Hill Science Plan the breeder gave me when I got him home. I had a few of the James Wellbeloved kibble in my hand and hand fed him them to tempt him. He never touched the Hill Science after that. Mixed in his bowl he would fish out the James Wellbeloved and leave the other behind.
I no longer offer any Hill Science Plan.
I wanted him on dry food as quickly as I could get him on it. Thankfully the breeder moved him from a wet meat to dampened Hill Science, slowly reducing the water content of it until they finally ate it just dry, ahead of them leaving at 8 weeks.
How old is your puppy? How exciting. When are you collecting your puppy?
LOL. I was far more excited about getting Harvey on the 18th than I was about Christmas the following week.
I picked Harvey up at 11am. I was hoping to get him a bit settled before his first night alone came around, but I'm sure others pick them up of an evening and still have no issue. Realistically it was probably just an excuse for me to gain an extra few hours of cuddles!
Best of luck with your puppy. I wish you many happy years together. Do you have a name yet?