Hi Sumangal,
Thank you for writing to Microsoft Community Forums.
Which device are you backing up the files to?
Normally, on the successful completion of back up, you will get the pop up saying that the backup operation completed successfully and if any file is skipped, you will be notified about it, however some files due to their length appear to be hidden. If you try to restore the file using File History it is actually there.
I would suggest to check if the files/folders are in the Excluded folder list. You may also want to check the file history logs to view the recent events errors, the option is available under Advanced settings of File History.
Finally, I would suggest to restore your personal files and see if the missing files are restored from the file history. Please refer to the following article. The article is for Windows 8, but holds good for Windows 10 as well.
Restoring files from File History
Hope the information is helpful.
Regards,
Peer Samie
Microsoft Community-Moderator