I suggest you contact the Yorkshire Terrier Club of Gt Britain. The secretary will let you have a list of breeders with stud dogs available that have had all the necessary health checks and you will be able to study pedigrees to find one that matches the lines of your bitch. When you find one you will be able to approach the stud dog owner to see whether your bitch matches their criteria for allowing one of their dogs to be used, has had all the necessary health checks and whether you have sufficient financial backing to provide for the bitch and puppies should anything untoward occur such as needing a cesaerian or having to hand rear the puppies should you lose your bitch in a complicated whelping, and whether your reasons for breeding meet with their approval.
Thats of course provided you want to breed to improve the breed rather than just to make money.