I would like to know how it is possible to modify the original folder so that it is in the same format (Year / album Title /Artist).
Many Thanks Bruno
You want to modify
\ExistingFolderName
into
\%year%\%album%\%artist%
like
\2026\Waterloo\ABBA
?
Maybe this FAQ topic "How to create directory structures based on the tags and move the files?" can help you using the 
Converter > Tag - Filename with a format string:
How to create directory structures based on the tags and move the files?
When you're using a backslash in a format string, Mp3tag will create a directory from the part of the format string in front of a backslash.
Here is an example that creates new directories under
D:\Music:
D:\Music\$left(%artist%,1)\%artist%-%year%-%album%\$num(%track%,2). %title%
The same is also possible using relative path names (instead of an absolute path in the example above) which creates the new directory below the current working directory:
%artist%-%year%-%album%\$num(%track%,2). %title%Please note, that the whole range of Mp3tag's Scripting Functions can be used in the format string.
If you only want to rename the current folder (and not move individual files from a shared folder to a new one) you could use
Convert>Tag-Tag for _DIRECTORY
Format string: c:\mymusic\%year%\%album%\%artist%
(replace the c:\mymusicpart with the real path to where the new folder structure should start)