In the DTU Purchase Model with "Standard". Business Critical is with General Purpose in vCore Purchase Model.
Migrating a database from the DTU-based purchasing model to the vCore-based purchasing model is similar to scaling between service objectives in the Basic, Standard, and Premium service tiers, with similar duration and a minimal downtime at the end of the migration process. A database migrated to the vCore-based purchasing model can be migrated back to the DTU- based purchasing model at any time in the same fashion, with the exception of databases migrated to the Hyperscale service tier.
https://docs.microsoft.com/en-us/azure/azure-sql/database/migrate-dtu-to-vcore?view=azuresql