After restoring windows 10, I found all my applications removed. I reinstalled eMClient, and all my subfolders are missing. Can my subfolders be restored?, Or can I restore the database. I am not finding the source files on my pc.
If the folders were on an IMAP or Exchange account, then they will be your email server. Log in using the web interface for the account and see what is there.
If the folders were created in Local Folders, or in a POP3 account, then they will only be on your computer. Sometimes when restoring Windows, there is a Windows.old folder (or similar) created on the C: drive. You can open that folder and navigate to the old C:\Users_yourusername_\AppData\Roaming\eM Client, folder.
With eM Client closed, copy the old eM Client folder to the same location on your new C: drive. You may have to enable hidden items in Windows Explorer to do that. That will restore the Local Folders and the existing IMAP or Exchange folder will sync with the server as soon as it connects.
It is always a good idea to make a backup (Menu > File > Backup) before replacing files in the database directory. If anything goes wrong you can just restore using Menu > File > Restore.