Welcome to Yorkie Talk and congratulations on your new pup! I brought Teddy home when he was 8 months old and he was strictly outdoor trained. I re-trained him to use pads as well.
Peeing on the pad he took to naturally, but he did not want to poop indoors. I had to corral him using baby gates in a smallish area with several pads lined up. Honestly, it was a sad exercise because he was so desperate to go outdoors to do his business. When he finally couldn't wait any longer, he did it. I praised him profusely, gave him a treat, and disposed of the pad immediately. When he saw how happy I was and that I cleaned up right away, then he was willing to keep doing it.
Admittedly, I had the advantage of having another Yorkie in the house to set an example for Teddy.
Here is my blog post with more tips that may help you:
Potty Training Small Dogs - Dog Life and Style
There are some people who use litter boxes, but I worry about the dogs potentially eating the litter. Pads are a more popular option.