Hi @ Vignesh G
As in this article, you only need DNS records for SharePoint Online if you use SPO to send emails externally.
https://docs.microsoft.com/en-us/office365/enterprise/external-domain-name-system-recordsIf not, then no DNS records. The URL of the SharePoint site will be based on the onmicrosoft.com domain when you first set up the 365 account. So if you called it myorg.onmicrosoft.com the SPO URL would be myorg.sharepoint.com
Hope that answers your question!
Best, Chris