As long as you have 2 digits for months and days,
select the column, do data>text to columns, click next twice,
under column data format select date and then select YMD
assuming that is the order of the original. Then it will retrun a date based
on your regional setting so if in US you should get MDY
Alternatively use =DATE(LEFT(A1,4),MID(A1,5,2),RIGHT(A1,2))
If needed you could insert a column for this, then use Copy followed by
Paste Special-Values to convert formulas to dates; now delete the original
column
best wishes
