The most critical point to understand is that downloading a 3DS BIOS file from any website is illegal. Nintendo holds the copyright to this proprietary software, and distributing it without permission is a violation of that copyright. The developers of emulators do not provide these files for this very legal reason.
First, let’s clear up a massive piece of misinformation. Strictly speaking, the like the PlayStation 1 or PlayStation 2. Older consoles had a Basic Input/Output System (BIOS)—a low-level firmware that initialized hardware. 3ds bios file download for android