Keep in mind that the Nintendo 3DS is region-locked . A European (EU) copy of the game will only play on a European 3DS console unless the console has been modified.
To play , your best legal option is to find a physical copy, as the Nintendo 3DS eShop was officially closed in March 2023. Download Harvest Moon 3D: A New Beginning (EU) ...
You can often find used European (PAL) copies on sites like eBay , Vinted , or local retro gaming shops. Keep in mind that the Nintendo 3DS is region-locked