You cannot install CIA files on a "stock" (unmodified) 3DS. If you haven't modded your system yet, the gold standard guide is 3DS.hacks.guide .
Always ensure the base Stretchmo app is installed before installing the DLC CIA. Even though the base game was free, the DLC acts as a "key" to unlock the levels. Stretchmo 3DS (USA) DLC CIA
Many users have uploaded "Ghostlight" or eShop "Redump" collections to the Internet Archive. Searching for "3DS DLC CIA Collection" often yields results for the entire library. You cannot install CIA files on a "stock" (unmodified) 3DS
A file is a package format used to install games, updates, or DLC onto a 3DS console using custom firmware (CFW). Even though the base game was free, the
Subreddits like r/3dspiracy have extensive megathreads and guides on how to safely find and install DLC for games that are no longer available for purchase. Safety and Requirements
Stretchmo (known as Fullblox in Europe) is the fourth game in the popular Pushmo puzzle series developed by Intelligent Systems. Unlike its predecessors, Stretchmo was released as a free download on the Nintendo eShop, giving players a set of introductory puzzles for free. To play the full game, users had to purchase "Attractions" (DLC packs) through an in-game menu. The DLC "CIA" Situation