from the Nintendo 3DS eShop. However, you can still download the game if you have previously purchased it or have a physical cartridge that needs updating. Nookipedia How to Download (Official Method)
Since March 27, 2023, it is no longer possible to purchase new digital copies Animal Crossing: New Leaf Animal Crossing- New Leaf -Normal Download Link-
If you already own the game digitally, follow these steps on your Nintendo 3DS: Open the Nintendo eShop from the Home Menu. Access Settings/Other by scrolling to the far left of the main shop screen. Select "Redownloadable Software" to view a list of your previous purchases. Animal Crossing: New Leaf and select "Download" to begin the installation. Updating to "Welcome amiibo" from the Nintendo 3DS eShop