Multiple date formats within a single column

I have an excel table with 13000+ entries of data. The first column has dates in the format of month/day/year, however, some of these dates are entered as text and some as numerical (I think). When I try to change the format to 'long date', the entries that are right aligned read as day/month/year (07/01/1959 will read as January 7, 1959 when it should read as July 1, 1959). The entries that are left aligned do not change into their 'long date' equivalents. I have tried playing around with the regional settings on my computer so that they will read as day/month/year but, nothing seems to work.

How do I format the column so that all the dates are in the same format and read as their proper 'long date' equivalents? I have attached an exert from the problem worksheet.data.xlsx

Turns out that the text to column approach worked. Except I chose fixed width instead of delimited. Thank-you