How can we use search.lookUp fields

 try {
                if (scriptContext.type === scriptContext.UserEventType.CREATE) {
                    let currentRecord = scriptContext.newRecord;
                    let salesOrderId = currentRecord.getValue({
                        fieldId: 'createdfrom'
                    });
if (salesOrderId) {
                            let salesOrderLookup = search.lookupFields({
                                type: search.Type.SALES_ORDER,
                                id: salesOrderId,
                                columns: ['custbody29']
                            });
                            let rmaId = salesOrderLookup.custbody29[0].value
}
}
catch (err) {
                log.error("error detected", err);
            }