
Hi @Ajay Mandal , welcome to Q&A forum!
Are you using classic experience or modern experience? If you are using classic experience, you could try to save site/list as a template, please refer to:
Save, download, and upload a SharePoint site as a template
However the functionality of saving a site as a template described in this article is only supported in SharePoint Server 2013, SharePoint Server 2016, SharePoint Server 2019 (classic sites only), and SharePoint Online (classic sites only).
It is not supported in SharePoint Online (modern sites) or SharePoint Server 2019 (modern sites).
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And per my knowledge, if you are using a modern page, you could go to Site Content> Site Pages library. Then set the permissions on a page level the same way you would set permissions on a document, folder or site.
i.e Click on the ellipses next to the page name and Share it with only one person.
A similar post:
How to set permissions on one page only in site?
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