How to extract data from an existing repeating section into a SharePoint column?

I have a SharePoint 2013 list that is using Nintex forms and has a repeating section that was not connected to a multiline of text from the beginning. I have created a workflow to get the FormData from the form and copy it to a multiline field. I then clean up the XML and want to get the values from my repeating section to use in other columns. The issue I’m having is that the XML is returning with extra information that I need to remove from the string. The code that’s returning is below

<?xml version="1.0" encoding="utf-8"?>
<FormVariables>
	<Version />
	<InvoiceRepeatingSection type="System.String">
		<?xml version="1.0" encoding="utf-8"?>
		<RepeaterData>
			<Version />
			<Items>
				<Item>
					<AccountNum type="System.String">5112</AccountNum>
					<CostCode type="System.String">5573</CostCode>
					<ProgramCode type="System.String">4649</ProgramCode>
					<DollarAmount type="System.Decimal">63.01</DollarAmount>
				</Item>
			</Items>
		</RepeaterData>
	</InvoiceRepeatingSection>
</FormVariables>

When I try to use this code in my query XML action the tree view doesn’t show the items and the test run returns the same exact code. My question is how can I extract the values from the item nodes or update my XML to remove the extra tags?