Sort not ordering product numbers as expected

Hi All

I am trying to sort some data into order, starting at S1000 through to S100145 but when I try it is not doing it the way I want it. They are product numbers. Codes starting S1000 - S1999 are one category, S2000 - S2999 are another and so on. But because it goes up to S10045 it is sorting S1000, S10000, S10005, S1001, S10010, S10015, S1002 and so on. Can anyone tell me what I need to do please.

Thank you in advance.

Beth

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