You can do this by going to Reporting > Custom Report.
In this area click new report. Then under display columns on the right click the features tab and tick to include 30 hour code.
You may also want to select a year groups on the left under filters so only pull through nursery students.
The report will have a column for 30 hour code which will show anything recorded against this field. To bring those students with a code entered to the top of the report click the 30 hour code heading twice.