Before this thread gets any more low-quality replies: no, an emulator for running games is simply just not possible.
More detailed answer:
It is possible to make a WiiU emulator for the 3DS, but it would be ridiculously slow, and you couldn't boot ANY game other than text-based homebrew, which probably wouldn't work either due to running out of RAM.
So basically, yes, it's possible, but you couldn't do anything with it, because there is just not enough RAM. The old3DS has 128Megs (of which up to 96Megs is usable in a special mode), and even on new3DS you can only use 172Megs out of the 256Megs. The WiiU has 2Gigs of RAM (of which only 1Gigs are usable to games), and let's not talk about VRAM...
Also, you'd have to emulate the GPU in software, because the 3DS GPU has hardware oversights which limit the max texture size to 512x512 (or 1024x1024 with many caevats).
It doesn't take a genius to see that even the new3DS has 10x less resources than what you'd need to even attempt this. I'm sorry, there are just things which are so far apart it's not possible.
As the others have said in their responses, this is exactly like trying to emulate a PS5 on an original GameBoy...
Edit: while you couldn't play the original game as-is on your 3DS, there is nothing (other than yourself and copyright laws) stopping you from spending many years of time making a recreation which can load the original (or downgraded) assets.