Start the iDevice Manager and click in the left menu "File Explorer".
The existing folders and files are displayed.
If you want to transfer the entire folder to the PC, right-click on it and select "Copy" in the context menu.
Now select the folder or desktop where the files should be saved.
If you want to copy one or more files from a folder, mark them in the list with the mouse.
Click in the top menu "Copy" or the same menu entry in the context menu.
You can also choose the target directory on your PC.