There are a total of 3 minecraft blocks available in Goat Bay City.
1 - From the beginning, go down the road, take a right towards the windmills into the "Slender" area to find a block in the cemetery.
2 - Head across town towards the blue skate park, and up the hill near a tree nearby, you'll find this block.
3 - Head towards the shore. You'll find a park to the left of the carnival, you can follow a dirt path towards a tree, finding the block directly beside it.
Collecting all 3 blocks will unlock the achievement.