SD/TF card error

Hi guys. I was hoping to get a little help with my problem here.When I put my R4 in my ds the SD/TF card error comes up. I read somewhere that I had to back up my files, reformat the SD card and then just put the backup files back into the SD card. The only problem is, how do I back up my files when my SD card doesn't open on the computer? My computer says that to open the SD card I will need to reformat it to a E:, but if I reformat it without backing up the files, my files will be deleted. It also says that there are 0.0 out of 0.0 mb on my SD card, so I'm afraid that somehow my data was already erased somehow.This error happened after I put in a file for Shin Megami Tensai 2. It was a 7z file but I changed the ending to nds and thought maybe that would work so I wouldn't have to unzip it with 7zip (yes, I know I'm stupid).I already read the other topic that was like this from 2009, but the problem is that they don't explain what to do if you can't backup your files from your R4 because it doesn't open on my computer.If anybody knows what happened or how to fix it, thanks in advance for any helpful comments you may have. I have a lot of completed games like Radiant Historia, Phoenix Wright, Rhythm Heaven, The World Ends With You and Professor Layton and the Curious Village on that SD card and I REALLY don't want to do all over again (lol).

I suspect your card has worn out and is no longer usable. You can try reformatting then running a data recovery program such as getdataback for fat, but be warned there's no guarantee it will work. If the format fails then the card has died and needs to be replaced.

OMG I'M SO SORRY FOR THE SUPER LATE REPLY DDDD:
Thanks so much for answering my question so quickly as well. I forgot about the question and then ended up spending a few weeks in my cottage where there's no internet lol
It kind of sucks to read that my card might not be fixed, but most of the games were completed anyways so it's not too much of a loss since I can just watch the endings off of Youtube or something.
This already happened to me once and the data recovery program I used didn't work last time, so I'm not to keen on trying it again; but who knows? It might work this time (if I'm lucky).
Again, thanks a lot for the reply :3