These are the caterpillar type enemies in the new dlc!
There's a hidden area in the map where these spawn constantly. At the start go right and a little up until you find a cave maze, follow it to the left and you'll pop out to a meadow area. Go up/right until you see the Sammies pop out of the walls. At the top of the Square area is an opening for you to go in and farm these kills out.
Here's a video on how to get to the location!
Sorry, this Game Clip has been removed
Ev Deadline posted a great map in the comments that pinpoints exactly where the spawn is! If you need more visual representation on where it is use that comment.
Just in case it gets lost:
https://primagames.com/tips/how-to-unlock-sammy-in-vampire-s...