You are correct.
You’ll have to write code to create the same directory structure used in the notebooks (e.g., /train, /valid, /test, /tmp, /models) that you see in the notebooks. From there you’ll have to move the images into sub-folders under /train … and from there, move a portion (20% or whatever) into /valid.
I also create a /sample directory and put a subset of everything in there for development. It makes it faster and allows you to debug things before using the full dataset.
You may want to look at the original part 1 notebooks as there is much more info there on how you can do the above.