Converting a date from mm/dd/yyyy to its numerical value

I am getting data from a reporting tool. The report contains Date and User columns (in that order). The tool returns dates in mm/dd/yyyy format.

Excel does not convert the imported data to a numerical date; it is stored as a text value (the raw data from the reporting tool is aligned to the left instead of to the right).

I need to concatenate User and the numeric date value (in that order). Using the raw imported data produces a result in the form userAmm/dd/yyyy instead of the needed format like userA42379. The concatenation of date as an unformatted numeric value only happens correctly if the raw data is in dd/mm/yyyy format (otherwise the input data is not interpreted as a date).

I tried to convert the dates from mm/dd/yyyy format to dd/mm/yyyy format using MID/LEFT/RIGHT and the number formatting in Excel but that didn't work. The date still appears in mm/dd/yyyy format when concatenated with another cell with text in it.

Any ideas?