FilePath="Archives/Annee/Mois"
In for each
--->FilePath.Split("/")
Use your Flow and pass the CurrenItem Variable in the Find Folder, It will work as per your Flow.
After For each loop, you can get the FolderArchieve which has the Last created folder data.
After you have created the first folder, you get a DriveItem as output. Use it to reference the folder when you create its child folder - no need for Find Files and Folders activity any more. Continue this way until the whole folder structure is created.