Dear Rupesh Shelke,
Good day! Thank you for posting to Microsoft Community. We are happy to help you.
Based on your description, I understand that you are asking how to add calendar on right side in new version of the outlook. Are you referring to the calendar on the right side to highlight the current day and displaying all Meetings/events and that can help you add a task? If so, to add that Calendar view in the new Outlook 365, you have to click on the My Day icon on the top right corner and make sure that is selected to show calendar all time, then choose "Calendar" as in the below screenshot.
If you are still unable to find the Calendar view, please let me know and provide more detail to understand what calendar you are referring to, I will be happy to assist you further. Please understand that our initial response may not always resolve the issue right away. However, with your help and more detailed information, we can work together to find a solution. Thank you for your help.