You will certainly have to use both STR_TO_DATE
to convert your date to a MySQL standard date format, and UNIX_TIMESTAMP
to get the timestamp from it.
Given the format of your date, something like
UNIX_TIMESTAMP(STR_TO_DATE(Sales.SalesDate, '%M %e %Y %h:%i%p'))
Will gives you a valid timestamp. Look the STR_TO_DATE
documentation to have more information on the format string.