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Dear YMahesh,
There may be no easy way doing that.
For example, if the website page is .html format, you may need some scripts to convert them to .aspx format for SharePoint Online.
For your reference: Convert .html pages to .aspx - Microsoft Q&A
For files in the website, you may need to manually download them and then use the OneDrive sync client to bulk-sync them to SharePoint Online.
The ideal way is to fetch the website data to SharePoint Online content such as the site list automatically by using Power Automate. However, you may create custom connectors with API.
So to fully migrate the website data, I think that it is better to do that with the developers in your company.
Thanks for your effort and understanding!
Sincerely,
Cliff | Microsoft Community Moderator