I know someone already suggested this, and I did try it. But when it prompted me to insert the original gamecard for reading data, it claimed I hadn't inserted one. I just assumed that meant it was failing to read the data, so I gave up. People had suggested an avalanche of hacks availiable, but I don't own a PC, so that was never a viable option. I just gave up. I would come back and look at the villagers walking around the town on the title screen, but that was all I could do. Time passed, I finally accepted that this part in my life was over, and I stopped looking at the village. Another piece of my childhood, dust in the wind - and that was the end to that mayor's journey.
Or so I thought. Almost a year later, something urged me to begin looking for answers again. I looked around, asked around on endless sites, and still nothing. I began looking in this thread again, and I decided I'd try the old solution again- I still had the other cartridge I bought to try last time, after all. I had just never had the will to make a new village. It just wouldn't be the same. So I open up, choose to import save data, and when prompted, take out the welcome amiibo cartridge and insert the original. I got the same result, saying nothing was there. Then, it hits me. I know blowing on a cartridge isn't recommended, but I was oofed anyways. I blow on the cartridge, then insert it. It reads. It saves the data, and prompts me to insert the welcome amiibo cartridge. I insert it. It transfers the data over. It goes back to the title. My town is there. I go to my file. It loads perfectly. I'm back. This last remembrance of my childhood is going to end someday- B U T N O T T O D A Y B O Y S , N O T TODAY
In case anyone else has to go through this, and by luck they find this: here's the simplified solution:
First, you'll have to purchase the retail version of Animal Crossing New Leaf: Welcome Amiibo. When you start up the game (if there is no existing town already) it will have the option to import save data. Go through the steps, import the data, and you can now access your data again, on the new cartridge.