Written a console for you. You can use it as per your need
static void Main(string[] args)
{
using (SPSite site = new SPSite("http://spserver:1111/"))
{
using (SPWeb web = site.OpenWeb())
{
SPList lib = web.Lists.TryGetList("TestLibrary");
SPQuery query = new SPQuery();
query.Query = "<Where><Eq><FieldRef Name='ContentType' /><Value Type='Text'>Folder</Value></Eq></Where>";
SPListItemCollection coll = lib.GetItems(query);
if (coll != null && coll.Count > 0)
{
foreach (SPListItem item in coll)
{
Console.WriteLine("Parent Folder : " + item.Folder.Name);
getChildFolder(web, item);
}
}
}
}
}
static void getChildFolder(SPWeb web, SPListItem item)
{
SPQuery query = new SPQuery();
query.Query = "<Where><Eq><FieldRef Name='ContentType' /><Value Type='Text'>Folder</Value></Eq></Where>";
query.Folder = item.Folder;
SPListItemCollection coll = item.ParentList.GetItems(query);
if (coll != null)
{
Console.WriteLine("\tChild Folder : " + coll.Count);
//foreach (SPListItem folderItem in coll)
//{
// Console.WriteLine("\tChild Folder : " + folderItem.Folder.Name);
//}
}
}
This will give you count for each parent folder.
Folder Structure in my library:

Output:
