SQL Database from Azure VM to Azure SQL Server : DB Size ( 300 GB DB)

What you need is called an “online” migration and Azure Data Migration Service (DMS) is the tool/service you need. This tutorial of the old version should help you do all the steps needed.

The new DMS uses Azure Data Studio and with the new version online migrations are supported only with Azure SQL Managed instance as target and not for Azure SQL Database as mentioned on this documentation.

I hope the old version still gives you the option for online migrations. If the old version does not allow you online migrations anymore, then what you are looking for is not currently possible.