I suspect you want a variation on the following
DECLARE @xmlData XML;
SET @xmlData = '
<results xmlns="http:www.xml.com/1" version="1" total-rows="34243" execution-time="0.6480239" entity-type="Case">
<columns>
<column id="Case.ReferenceNumber" data-type="ReferenceNumber">Reference Number</column>
</columns>
<rows>
<row case-id="8cf25fe3-9312-4821-bbc9-2a447bac5e25" case-reference="TEST - 0032218" case-status="closed">
<data column-id="Case.ReferenceNumber">Test1- 0032218</data>
</row>
<row case-id="86a41221-3cb2-4725-a79a-fb825acada51" case-reference="TEST - 0032318" case-status="Open">
<data column-id="Case.ReferenceNumber">Test2 - 0032318</data>
</row>
<row case-id="5c7f8c99-86f9-41a1-b2a1-376874e7f2de" case-reference="TEST - 0032418" case-status="closed">
<data column-id="Case.ReferenceNumber">Test3 - 0032418</data>
</row>
</rows>
</results>';
INSERT INTO XmlData (CaseID, CaseReference, CaseStatus, ReferenceNumber)
SELECT
r.value('@case-id', 'UNIQUEIDENTIFIER') AS CaseID,
r.value('@case-reference', 'NVARCHAR(50)') AS CaseReference,
r.value('@case-status', 'NVARCHAR(20)') AS CaseStatus,
r.value('(data[@column-id="Case.ReferenceNumber"]/text())[1]', 'NVARCHAR(50)') AS ReferenceNumber
FROM @xmlData.nodes('/results/rows/row') AS XTbl(r);
Obviously, you would replace the hard coded declaration, but this should be okay for you.