Cubik Studio

If you import it after modeling and apply the resource pack, this is how the error occurs. How do I solve it

When you're making models all the files are best placed in a the location they'd be in a real resourcepack, that way Cubik will know the correct path when importing textures, etc.

You can fix it 2 ways:
Re-import the texture in the correct location from the resourcepack and then re-export the model;
Or edit the exported json file's texture path to be correct (usually something like minecraft:textures\item\iron_sword )