Hello Sanjay R, welcome to Microsoft Q&A forum.
First, head to https://account.microsoft.com/services to see if you have the correct Microsoft 365. You need to have Microsoft 365 Personal or Family to see new Copilot features. "Classic" subscriptions do not include Copilot features.
Then, follow this Microsoft tutorial to enable all prerequisites for the Copilot button to appear : https://support.microsoft.com/en-us/office/how-to-find-and-enable-missing-copilot-button-in-microsoft-365-apps-c8482b93-4b96-4bb8-8ec9-5148f4d42441
If you have the Connected experiences disabled, you will not see the Copilot button.
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