Since you're running a microflow inside the queue, it will determine when the microflow is exectuted. Further more the microflow is not executed as the current user so showing a page or message is not possible.
You may be able to create an extra object inside the queue and once it's finished it is presented via a “chat/message” kind of thing to the user
Hi Aditya,
As Roy mentioned, it is not possible to show message and/or show page from inside the microflow which runs in a task queue as that has no user context.
I’d recommend to re-think on what you/user want to achieve.
Good luck!