Cannot get the right date string format

HI @Lori

You can dive the date formats in the array of strings in the below expression.

DateTime.ParseExact(aa,{"yyyy-MM-dd","yyyy/MM/dd"},System.Globalization.CultureInfo.InvariantCulture,System.Globalization.DateTimeStyles.None).ToString("yyyy-MM-dd")

You just need to add the formats in the array if in case any other formats

Regards
Sudharsan