A useful item for those looking to turn their Barpau into Milobellus into Pokémon Sword and Shield is Bel'Ecale. It's a small item that you need to give to your Barpau, then trade that Pokémon with a friend to evolve it into Milobellus. When it evolves, you can receive it again and add it to your collection.
To find the scale, you have a handful of options at your disposal. The first is located on Route 2. However, you cannot do it early. You have to wait for the Rotom Bicycle update to be able to travel in water. When you have it, return to route 2, go to the professor and go west of the house. Cross the water to the island. Once there, head northwest and you should see a distinct sparkle in the water near the other piece of land. Go ahead and grab your first beautiful scale.
You have the chance to locate bel ecaille at another location, the South Lake Miloch, inside the Wild Area. You need to scour the southern part of the area looking for similar chaff in the water. It's not a guaranteed drop, but if you check the area regularly you should find it after a handful of rotations.
Once you have purchased the item, you are good to go and you can freely trade your Barpau with one of your friends who will trade them to you. We also know where you need to go to find a Barpau.