It's a matter of breaking it down into component parts.

You need to get the year, month, and day out of the date value.

Then you need to combine those into a single value.

Finally you need to convert it to an integer (since trying to concatenate the output of a DATEPART results in math).

The additional complication is that month and day outputs do not have the leading zeros you want.

Add a Derived Column transformation and try this expression. Of course replace the YourDateField with your field name.

(DT_I4)((DT_WSTR,4)YEAR(YourDateField) + (LEN((DT_WSTR,2)MONTH(YourDateField)) == 1 ? "0" + (DT_WSTR,2)MONTH(YourDateField) : (DT_WSTR,2)MONTH(YourDateField)) + (LEN((DT_WSTR,2)MONTH(YourDateField)) == 1 ? "0" + (DT_WSTR,2)DAY(YourDateField) : (DT_WSTR,2)DAY(YourDateField)))

Edit - Just realized this was threadomancy on the previous post but it's still valid as a solution to a general problem.