Revise paste listar archivos con carpeta padre

var conjunto = 1;
  var limite = 400;

// no tocar 
  var contador = 0 + (limite*(conjunto-1));
  var skip = limite*(conjunto-1);
  var skip_c = 0;

function listFilesAndFolders(){
  var folderId = Browser.inputBox('Enter folder ID', Browser.Buttons.OK_CANCEL);
  if (folderId === "") {
    Browser.msgBox('Folder ID is invalid');
    return;
  }
  getFolderTree(folderId, true); 
};

function getFolderTree(folderId, listAll) {
  try {
    var parentFolder = DriveApp.getFolderById(folderId);
    var file, data, sheet = SpreadsheetApp.getActiveSheet();
    if(conjunto == 1) {
      sheet.clear();
      sheet.appendRow(["Folder","Name", "URL"]);
    }
    getChildFolders(parentFolder.getName(), parentFolder, data, sheet, listAll);
  } catch (e) {
    Logger.log(e.toString());
  }
};

function getChildFolders(parentName, parent, data, sheet, listAll) {
  var childFolders = parent.getFolders();
  while (childFolders.hasNext()) {
    var childFolder = childFolders.next();
    var files = childFolder.getFiles();
    while (listAll & files.hasNext()) {
      var childFile = files.next();
      if(skip_c <= skip) {
          skip_c+=1;
      } else {
        contador+=1;
        if(contador<=conjunto*limite) {
          data = [  childFolder.getName(),
            childFile.getName().replace(".pdf",""),
            childFile.getUrl(),
          ];
          sheet.appendRow(data);
        } else {
            return;
        }
      }
      
    }
    getChildFolders(parentName + "/" + childFolder.getName(), childFolder, data, sheet, listAll);  
  }
};