Hi,
I'm not using currently AAD nor the Employee ID column, although from a brief research it seems like it should work with just correct setup of synchronization, and mapping of extension attributes, as from what i've found Employee ID is an extension attribute.
Open up this* window in Designer studio, in Columns Mapping add in employeeId** column, run the sync, and check if the data is fetched :)
* https://docs.webcon.com/docs/2026R1/Studio/SystemSettings/GlobalParams/UserSynch/SynchConfig/
** https://stackoverflow.com/questions/71146267/get-employee-id-from-azure-active-directory, https://learn.microsoft.com/en-us/entra/identity/app-provisioning/index-employeeid-attribute-entra-id-to-active-directory