NumberFormat Property
From Microsoft Graph Visual Basic
NumberFormat Property
Returns or sets the format code for the object. Returns Null if the cells in the specified range don't all have the same number format. Read/write String for all objects, except for the Range object, which is read/write Variant.
expression.NumberFormat
expression Required. An expression that returns one of the above objects.
Example
This example sets the number format for the data labels for series one.
myChart.SeriesCollection(1).DataLabels.NumberFormat = "General"