Do not buy puppies from a puppy miller, especially in Amish country. You will end up with a pup that can have a myriad of problems, from behavioral issues, to physical problems. And never by a pup from a retail store. Reputable breeders DO NOT sell their pups to retail stores.
Things to know about reputable breeders:
They do not breed the female every year. Every other year so as not to overbreed the female.
They will raise the pups indoors, not in an outside kennel. This helps the pups become socialized.
They will invite you to meet all the pups in the litter as well as the female and sire. Although sometimes the sire is not on site, as the breeder may contract out for stud services.
They will not let you take the pup home before it is weaned at no younger than 8 weeks of age.
They may ask you to sign an agreement to have the dog spayed/neutered.
The American Kennel Club is one resource for breeders: https://marketplace.akc.org/
You can also ask your veterinarian if they have any connections to a good breeder.
Or, you can save a ton of money and adopt from a shelter or rescue organization.