You can export from v11 to csv and import into v12 using the import tool. You can't migrate data only as there is no safe landing place for the data without migrating the configuration.
I am still having problems I export to a csv from version 11 then set a task to import to version 12 then I et (Error Type Line 1 The value Date Submitted does not have the correct date format (yyyy-MM-dd’T’HH:mm:ss:.SSS) for the Created on Field. I have done several csv files and formatted the column with the format asked for but still get same error. Any Ideas?
Can you show an example of your data? It is likely missing the 'T'.