To begin with, the breeder let your baby go way too early. (That's besides the point, but I wanted to put that out there for any others that may be reading these threads.)
Yorkies take a year or more to grow out their coat to floor length. There are some with wiry coats that may not ever reach full floor length, though. But at 6 weeks and even 3 months, it's too early to know for sure if your baby's coat will grow very long. You'll just have to wait & see!
That's why yorkies are so much fun to watch grow...you never know what you're gonna get.
