afshinmokhtari,
Media Library Plus include a second plugin, Media Library Plus Reset that you will see on the Plugins page. To use it, deactivate Media Library Plus, activate Media Library Plus Reset and click on the Reset Database in the menu. This will clear out the existing MLP data. then deactivate Media Library Plus Reset and reactivate Media Library Plus which will now rescan your media library data.
Then when you go to Media Library+ then you should see a folder tree on the left and the folder contents on the right. If the folder tree fails to load it is because there is a error in your image data. Sometimes it is necessary to first run the Better Search and Replace plugin to correct any URLs that have the wrong address, especially if your site has been moved to a new domain, and then run Media Library Plus Reset.