Hello Aspirant,
After you pass class 10th or class 12th you get your passing certificate from your respective school, so as you have passed class 12th so you should get the passing certificate issued by CBSE and it will not be available in Digi locker because the certificates are only provided through your school. So regarding passing certificate, Migration certificate, character certificate contact your school authorities they would provide you all such certificates.
I hope this information helps you.
Good Luck!!
Regular exam updates, QnA, Predictors, College Applications & E-books now on your Mobile