Google Script to get file counts.

filecount.gs

/** 
 * Google Apps Script - List all files & folders in a Google Drive folder, & write into a speadsheet.
 *    - Main function 1: List all folders
 *    - Main function 2: List all files & folders
 * 
 * Hint: Set your folder ID first! You may copy the folder ID from the browser's address field. 
 *       The folder ID is everything after the 'folders/' portion of the URL.
 * 
 * @version 1.0
 * @see     https://github.com/mesgarpour
 */
 
// TODO: Set folder ID
var folderId = '<put folder id here>';
 
// Main function 1: List all folders, & write into the current sheet.
function listFolders(){
  getFolderTree(folderId, false);
};

// Main function 2: List all files & folders, & write into the current sheet.
function listAll(){
  getFolderTree(folderId, true); 
};

// =================
// Get Folder Tree
function getFolderTree(folderId, listAll) {
  try {
    // Get folder by id
    var parentFolder = DriveApp.getFolderById(folderId);
    
    // Initialise the sheet
    var file, data, sheet = SpreadsheetApp.getActiveSheet();
    sheet.clear();
    sheet.appendRow(["Full Path", "Name", "File Count", "Last Updated", "Size"]);
    
    // Get files and folders
    getChildFolders(parentFolder.getName(), parentFolder, data, sheet, listAll);
    
  } catch (e) {
    Logger.log(e.toString());
  }
};
function getFolderFileCount(folder)
{
  var files = folder.getFiles();
  var count = 0;
  
  while ( files.hasNext() ) {
    count++; 
  }
  return count;
}
// Get the list of files and folders and their metadata in recursive mode
function getChildFolders(parentName, parent, data, sheet, listAll) {
  var childFolders = parent.getFolders();
  
  // List folders inside the folder
  while (childFolders.hasNext()) {
    var childFolder = childFolders.next();
    var files = childFolder.getFiles();
    var count=0;
    while(files.hasNext())
    {
      count++;
    }
    // Logger.log("Folder Name: " + childFolder.getName());
    data = [ 
      parentName + "/" + childFolder.getName(),
      childFolder.getName(),
      count,
      childFolder.getLastUpdated(),
      childFolder.getSize()
    ];
    // Write
    sheet.appendRow(data);

    // Recursive call of the subfolder
    getChildFolders(parentName + "/" + childFolder.getName(), childFolder, data, sheet, listAll);  
  }
};