convert date in General format to date that can be sorted

The dates in your sample are text strings and not real dates/numbers. The key to getting sortable dates is to get the dates stored as numbers. As long as they are stored as numbers, they should be sortable. Note that number format should have no impact on sort order. Common strategies for converting number stored as text to numbers: https://support.microsoft.com/en-us/...rs=en-us&ad=us

In your sample, I was able to use Text to Columns to convert the text to numbers. Where you're in England and your operating system may have different default date/time settings, you may have to specify MDY dates at step 3 of the text import wizard or otherwise experiment to make sure you can reliably convert the text to date/number. ISTEXT() is a useful function for determining if the text to number conversion worked.

Once the dates are correctly stored as numbers, you should be able to readily sort them. If you prefer a ddmmyyyy number format, you should be able to apply that as a custom number format code.