In order to accomplish what you're looking for you need to create a new empty table with the autonumber, then run an INSERT statement with the ORDER BY instruction attached. This will ensure that the data gets numbered appropriately.
You will then need to do whatever table rename is relevant.
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Your lack of planning does not constitute an emergency on my part...unless you're my manager...or a director and above...or a really loud-spoken end-user..All right - what was my emergency again?