You can buy a dematter comb, and slowly work out the matts , using your fingers, separating the matts , and using the demmater comb. It takes patience. Use a conditioning spray to soften the hair . It is very important not to try and dematt your baby's hair without using a conditioning spray first .
Also, please bruse your baby's hair with a slicker brush. these are wonderful, and are maintence brushes. It is important to brush your yorkies hair on a daily basis to prevent serious matting.
my Suzi had to be shaved down once because of this, when I became very sick in the hospital. I understand, that it can be difficult to maintain the grooming. It takes a long time for the hair to grow back > I had to learn the hard way.
A puppy cut looks cute on a yorkie. Most groomers are familar with this style . Take your yorkie to a groomer who is experienced with yorkies and is experienced as a groomer. This is Very important .