how do i edit a mod/ turn it into a project file?

Mcreator can only edit files with the MRC tag.

You should have kept a backup.

@#1.1
Ok, first of all, do not be so rude. 
Now, I will give the answer that you most likely want to hear: You can technically restore your project files from the mod file itself.
But I bet you will not want to do after you read the process. 
Pretty much simply, first you need to decompile your mod. You can download some decompiler, or you can use some online (but these usually have some limitations or some other issues).
Now you have your decompiled mod, the main problem now is that all Minecraft names of fields, methods, and classes are obfuscated. You have to get MCP mappings of your MCreator and translate them manually or you can use for example  mcpbot  to getting the translated names. Also, there is a third most likely third option of using a tool that should do the work for you. I have seen a person on MCF talking about, so go ahead and search for it.
The final step is going to be most likely getting these files to MCreator. There are few places where you have to put them. Also in some locations you need .class files, and in some .java files.

Sorry @Purple Slimez.. I wasn't trying to be rude..

What i was trying to say, is that even if it is possible, the mod wouldn't come out the same. There would be hundreds of issues with the .jar decompression, and it would most likely be better to make a new mod rather than getting that one.

PS. Always keep a backup.