Assumptions:
1) the column had a name such as someDate
2) the column is extracted as character rather than date, datetime or the like
3) the days portion of the field always has 2 digits; only the month portion has an optional leading zero, implying the field will always have a length of either 5 or 6
LEN(someDate) == 5 ?
'0' + SUBSTRING(someDate,1,1) + ' ' + SUBSTRING(someDate,2,2) + ' 20' + SUBSTRING(someDate,4,2)
:
SUBSTRING(someDate,1,2) + ' ' + SUBSTRING(someDate,3,2) + ' 20' +
SUBSTRING(someDate,5,2)