Hi Mahsa Thank you for your question.
To choose the service objective, or compute size, for the migrated database in the vCore model, you can use a simple but approximate rule of thumb: every 100 DTUs in the Basic or Standard tiers require at least 1 vCore, and every 125 DTUs in the Premium tier require at least 1 vCore. as mentioned in the doc Choose the vCore service tier and service objective.
To convert from the DTU-based purchasing model to the vCore-based purchasing model, see Migrate from DTU to vCore.
Please let me know if that helps.
Regards,
Oury