@narveersingh26 The files in your image refer to an Olde Opera version (12.18 or earlier). I assume you're still using Olde Opera and your question refers to it?
The dates for many of your other Opera personal files range over a 13 January 2018 to 1 March 2018 period. Your bookmarks.adr file (plus several others) dates from 14 August 2017. The bookmarks.adr file shown in your image, being only 3kB in size, implies it contains only a few entries. If it was a significantly larger file as you remember it, then something either caused an earlier and larger bookmarks file to be overwritten with the present small version on 14 August 2017, or the larger bookmarks file was significantly corrupted and shortened. If a bookmarks file gets corrupted (either by a browser crash, a system crash, a drive problem, or an OS error), Olde Opera would over-write it with a new, default (empty) copy when Opera was restarted. That may well be what happened in your case.
If it were my system, I'd consult my backup files for an earlier, backup-copy of the bookmarks.adr file (assuming you created a backup and it still exists). If no backup exists, then if you are using a Windows version that automatically keeps shadow-copy records, in File Explorer, try right clicking the bookmarks.adr file in your image, select Properties, then select the Previous Versions tab to see if an earlier file copy may have been preserved in that way. If none of this applies, you're probably facing the complete loss of the original file contents.