Hi @srikanth kasula , thank you for posting in the Q&A forum.
Exporting the data from SharePoint Viewers feature to Excel is not yet supported in SharePoint Online.
If you need the usernames of File Viewers in a site or in this tenant, I suggest using the Site Usage report instead. It gives a rapid idea of who has recently viewed files or pages without providing the detailed files or pages, and supports exporting to Excel.
You can find the related report as a Global/SharePoint admin via Microsoft 365 admin center > Reports > Usage > SharePoint files > View more.
You can refer to the references below for detailed information:
Microsoft 365 Reports in the admin center.
Microsoft 365 Reports in the admin center - SharePoint site usage.
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