New IPhone 12

When I bought the IPhone 12 yesterday, the tech downloaded all my old IPhone 6+ data to the Cloud in order to be transferred back to my new phone. He then clicked through the questions the new phone asked and it looked like everything had downloaded. Unfortunately, when I got home I noticed a couple things did not transfer back, e.g., my "Notes" (very important), most of my "Music" and my Email messages. Can you walk me through how to find the old files on the Cloud and how to them download them to the new phone?