Hi neighbor (i'm in clifton
)!
The attachment you use depends on the clippers you have, type of coat your yorkie has, and what length you would like to leave on your yorkie. The term "puppy cut" just means same length all over. It can range from a short almost shaved look to a few inches of hair left on.
If you have your own attachments just start with the longest one and go smaller until you find the length you want. If you have a silky coated yorkie and you want a longer puppy cut, remember to clip in the direction of the hair growth. If you want a tighter, shorter cut you can take a long attachment and go against the direction of hair growth. This will take the hair shorter then the mm written on the comb as length.