I found out how to replace 3ds apps with others and the 3ds's main file system for an idea for homebrew for the 3ds.
The problem is im a child and I don't know to program anything

But here's the linking for the files to delete and replace with a hack (the Nintendo video channel linking)
apps are installed to sd card only making the hack easier
Nintendo 3DS/b39247d444f773efa1313eccabfdc6c5/7f2f00b34760a166534430320002544d/title/00040000/0004ab00/content

create a app with same endings do not delete cmd otherwise won't read in 3ds

First of all, if it isn't Wii-related, it belongs in Off Topic.

Secondly, what you have shared here is well known and is documented over at [3dbrew.org]. It is also largely useless. The files are encrypted/signed with several keys we don't have access to (I think they're encrypted with the common key and signed with a key unique to a particular console. Probably private key and SD key as well. I don't know much about cryptography etc.). This means it is impossible to replace anything without the 3DS rejecting it. There is also not enough information about the hardware etc. to be able to create working code the processor in 3DS - this would require reverse engineering of existing code, which requires the code to be decrypted, which would need the common key at the very least, possibly a few others as well.

Did you really think it would be as simple as replacing a couple of files on the SD card? Nintendo are nowhere near that stupid.

Quote:

SifJar
The files are encrypted/signed with several keys we don't have access to (I think they're encrypted with the common key and signed with a key unique to a particular console. Probably private key and SD key as well. I don't know much about cryptography etc.).

*All* files under /title are encrypted with a console-unique key, which is mentioned on the page you linked to.(doubt commonkey is used at all for those files, I'd assume no extra crypto/signing besides the console-unique key is used as well)

Well, as I said, I know very little about cryptography. Thanks for the clarification.