You must deploy sufficient NSX Edge node resources to replace the Edge Services Gateways in the NSX-v environment.
You can use the first step of migration, Import Configuration, to find out the number and size of NSX Edge nodes that are needed. See Import the NSX Data Center for vSphere Configuration.
Config translation failed [Reason: [TOPOLOGY] Can not proceed with migration: Existing NSX-T environment has 0 Edge Node(s). In order to complete the migration successfully, the environment must have 4 Edge Nodes of size MEDIUM.]
If you see this message, click Rollback to roll back the migration. Deploy the appropriate number and size of NSX Edge nodes, and restart the migration.