12/23/2018
1/12/2018
You cannot sort such muddle without first converting or reorganising it.
Assuming your “alphanumeric numbers” are dates given as texts in the funny mid-endian format stubbornly used in the USA, I can only advise to convert them into the numeric standard representation of dates in spreadsheets.
If the strings you have are placed in one column, this is simple: Select the respective range of a single column and choose >Data>Text to Columns... from the menu. In the dialogue that opens deselect any separators. Then click on the header of the one column shown in the dialogue and choose as the column type Date (M/D/Y). Then click OK.
If you once want to export dates as text strings use exlusively the format YYYY-MM-DD. It is the only date format meeting all the needs. Being strictly regarding “decreasing significance” it is even eligible for correct sorting without conversion to numbers. Mainly, however, it is unambiguous and human-readable, and thus suitable for global communication. (The format is standardised by ISO 8601.)