Q: Help to convert numbers file to xls

In numbers: Use the export command, xls is but one of its options.

following up with CSound, you should use the menu item "File > Export To > Excel…":

'Export to Excel...' is useful for sharing data, particularly if it is contained in one Numbers table. But bear in mind that you may not be entirely happy with the results if you have more than one table or a lot of formatting. The structure of the Excel document may be different from what you (or Excel user recipients) expect.

SG