Go to Opera Menu > About and it will tell you where your profile folder is located. Since your destination system is Windows 8.1 you can just copy the whole folder over and replace. Be forewarned; if you replace the folder it will erase anything you have in your profile on the destination machine. This includes bookmarks, speed dials, passwords and the like.
Malwarebytes and Hitman Pro. Is these both useful programs for Opera to use.
Kindly, suggest me that what these programs are and how often or how to use it?
Both programs are useful, independent of whatever browser you use. These are free adware removal tools that are normally downloaded and manually run by the user to scan their system for adware or potentially unwanted program (PuP) infections. They will produce a list of the adware found on the system, if any, and will allow the user to command them to remove the adware. Even after successfully using such programs, a user is still wise to also check his desktop shortcuts for his browser(s) to make sure the adware hasn't added its own http address to the shortcut command code. In some stubborn cases, the user may also need to manually remove the adware from a browser's extension or add-in listing from within the browser.
Adware, much like malware (viruses, etc), is constantly being changed by its makers to avoid easy removal by an infected user. So a particular anti-adware program may not always detect a certain brand or version of adware, hence the need to sometimes try more than one anti-adware program. Likewise, it's the reason the user may have to do some added manual removal or fixes, as noted above, in addition to using the anti-adware programs.