Due to changes in the index structure data domains from 3.0 can not be directly imported into 3.1. If you still have the source data you can reload it via Integrator ETL or ODI. If not it is possible to leverage the web-service component in Integrator to export the records for serialization to disk or directly writing to a 3.1 instance.
Ryan S. - EID PM
Okay, thanks I am going to reload the data through ETL