Loop through subfolders to join pdf in each folder

Dear kind Developers, hereby i have a folder which contain subfolders like below:

each folder contains subfolder like below
and each subfolder contains pdf which i need to join:
the same goes to every other folders. i need to loop through each subfolders and join pdf on each folder and store that pdf on that folder itself. i can use the join pdf activity but i am confused how to loop through each subfolders to join the pdfs. thank you so much in advance.

Refer this workflow.
Folder.xaml (5.8 KB)

Main.xaml (10.2 KB)
This is the same requirement i had and created a process hope it helps. just change the folder path as per your requirements in the variables.