Press F12
or go to Format → Lists → Numbered List.
The macro recorder (Tools → Macros → Record Macro with macro recording enabled under Tools → Options → Advanced) is often problematic, but it does well in this case.
document = ThisComponent.CurrentController.Frame
dispatcher = createUnoService("com.sun.star.frame.DispatchHelper")
dim args1(0) as new com.sun.star.beans.PropertyValue
args1(0).Name = "On"
args1(0).Value = false
dispatcher.executeDispatch(document, ".uno:DefaultNumbering", "", 0, args1())
A more complex numbering macro using com.sun.star.text.NumberingRules is given at [Solved] Starbasic Macro for bullets and numbering look (View topic) • Apache OpenOffice Community Forum.
EDIT:
Here is a macro to convert the selected numbered list to ordinary paragraphs with the label numbers.
Sub ConvertNumberedListToLabels
oSel = ThisComponent.getCurrentController.getSelection()
oSelEnd = oSel.getByIndex(0).getEnd()
oCurs = ThisComponent.getText().createTextCursorByRange(oSelEnd)
oCurs.gotoStartOfParagraph(False)
While oCurs.NumberingIsNumber = True
labelString = oCurs.ListLabelString
oCurs.getText().insertString(oCurs, labelString & " ", False)
oCurs.NumberingRules = None
oCurs.gotoPreviousParagraph(False)
Wend
End Sub