Hi @Nilesh Patel Thank you for posting your Question on Microsoft Q&A.
DMA is needed if you want to assess before migration with DMS. Alternatively, if you use the Azure SQL Migration extension in Azure Data Studio, you can run assessments and migrations in a single place. The Data Migration Assistant provides seamless assessments of SQL Server on-premises and upgrades to later versions of SQL Server or migrations to SQL Server on Azure VMs or Azure SQL Database. It also help you helps you upgrade to a modern data platform by detecting compatibility issues that can impact database functionality in your new version of SQL Server or Azure SQL Database.
Please see the Migration guide : SQL Server to Azure SQL Managed Instance.
Please let us know if you need additional Clarification
Regards,
Oury