to run the below command , start PowerShell in visual studio. Select the database project.
In PowerShell:
Script-Migration
this command will generate script from blank database to the latest migration.
Script-Migration migrationname1
this command will generate script from migration named migrationname1 to the latest migration.
Script-Migration migrationname1 migrationnamex
this command will generate script from migration named migrationname1 to migrationnamex