Hello @Arijit Saikia
See for all client instance user record data population happens in different style it can happen through LDAP/AD/Workday/Sailpoint integration.
Now I am not sure how it's happening on your instance so first identify same then check when user records are created how cost center data is populated is it while creation or is there any other business logic kept in which populate this data. Once you have this information then try to check when this cost center data is created what all details come in then try to create missing record information manually or if possible try to get data from thirdparty if any integration is in place. Now once this data is available then you identify which records are affected and try to update them all before doing an update try to do on 3-4 records once you are confident proceed with bulk affected records.
If my response has helped you hit helpful button and if your concern is solved do mark my response as correct.
Thanks & Regards
Viraj Hudlikar.
