Modify2.swift

func collectionView(_ collectionView: UICollectionView, cellForItemAt indexPath: IndexPath) -> UICollectionViewCell {
    let cell = collectionView.dequeueReusableCell(withReuseIdentifier: "DragDrogCollectionViewCell", for: indexPath) as! DragDrogCollectionViewCell
    let index = indexPath.section * ViewController.columnCount +  indexPath.row
    cell.backgroundColor = UIColor.clear
    cell.label.text = ""
    if (index < cellDataList.count) {
        cell.backgroundColor = UIColor.yellow
        cell.label.text = String(cellDataList[index])
    }

    return cell
}

func collectionView(_ collectionView: UICollectionView, itemsForBeginning session: UIDragSession, at indexPath: IndexPath) -> [UIDragItem] {
    let dataIndex = getCollectionViewColumnMaxCount() * indexPath.section + indexPath.row
    guard (dataIndex < self.cellDataList.count) else {
        return []
    }

    let attributedString = String(indexPath.item)
    let dragItem = UIDragItem(itemProvider: NSItemProvider(object: attributedString as NSItemProviderWriting))
    dragItem.localObject = attributedString
    return [dragItem]
}