This will just be a matter of time as you progress through the game.
The building you need are as follows;
Your Home
Bakery
Town Hall - When you enter, take the left exit to find a secret room.
Angus’ Shop
Amelia’s House
Francis’ Shack
Viktoria’s Mansion
Angus’ Trailer
Steve’s Tent
Museum - Please make sure to head inside the separate rooms for Bugs, Shells and finally Fish to unlock this achievement.