Are you sure it’s not “resources/3dfiles/excavadora_2/plaquita.3ds”?
Because backslashes represent an escape character.
You can get the filename like so:
var mypath : String = "resources/3dfiles/excavadora_2/plaquita.3ds";
var parts : Array = mypath.Split("/" [0]); //create array using "/" as delimiter
var nameAndExtension = parts[parts.length-1]; //get last element of array
var fileName = nameAndExtension.Split("." [0])[0]; //remove extension
Debug.Log(fileName);
var mypath = "resources/3dfiles/excavadora_2/plaquita.3ds";
var lastIndex = mypath.LastIndexOf("/"[0])+1;
var fileName = mypath.Substring(lastIndex, mypath.Length-lastIndex-4);
print (fileName);
Assuming that you know the extension is always 4 chars including the “.”