Hi,
Try below code.
wt.change2.WTChangeOrder2 thisNotice = (wt.change2.WTChangeOrder2) primaryBusinessObject;
com.ptc.core.lwc.server.PersistableAdapter obj = new com.ptc.core.lwc.server.PersistableAdapter(thisNotice,null,null,null);
obj.load("IFRQ_Number");
String IFRQ_Number= (String) obj.get("IFRQ_Number");
Thanks,
Kaushik