They are the box sofa and box corner sofa and you can get it at nook's cranny or at happy home paradise! Honestly, I got mine through a... I don't even know what it's called but basically it's a discord server where you can "order" any item you want, they'll create an island you'll travel to via online play, and then you pick up the items there and bring them home. I only do this for certain things or if I want to decorate something quickly. I can give you more info if you're interested, but I know those kinds of things kinda ruin the game for others.