windows - How to convert a tree directory into a single level directory

This question might be confused , it's better to show some example.
I have a folder that contain many sub-directory which might be multiple level.The structure below show the folder , all folder do contain their own file.

mainFolder
|--a
|--|--ab
|--|--ac
|--|--ad
|--b
|--b
|--|-cd
|--d

The above is the tree structure of mainFolder. I am trying to write a batch file that able to convert the whole tree into a single level structure.

--a
--ab
--ad
--b
--c
--cd
--d

Above is the expected output. All file should be in their own folder.

setlocal EnableDelayedExpansion
set "targetPath=%~dp0mainFolder"
for /r "%targetPath%" %%i in (.) do (
     echo %%i
)
pause

This is my current code , which able to loop through and display the absolute path of the directory

Answer

There are inconsistencies: in source --c is missing in dest there is no --ac

Source tree:

> tree
└───mainFolder
    ├───a
    │   ├───ab
    │   ├───ac
    │   └───ad
    ├───b
    ├───c
    │   └───cd
    └───d

Provided mainfolder is in the root of the drive this single cmdline:

@for /r "\mainfolder" %A in (.) do @for /f "tokens=5 delims=\" %B in ("%A") do @move "%A" "\mainFolder"

Will produce this destination tree:

> tree
└───mainFolder
    ├───a
    ├───ab
    ├───ac
    ├───ad
    ├───b
    ├───c
    ├───cd
    └───d

If not adjust the tokens value from 5 to match the dirlevel.
In a batch file double all the percent signs %%