Do I need a court order if I have a notarized letter revoking temporary guardianship of my child?

I have guardianship papers saying I am now my biological child's guardianship to me from my child's mother who us locked up in prison. I also have the letter revoking temp guardianship of the lady who has my child. I was told by the prison I could take the papers to the police & they'd go get my child. But when I got there they said I need a court order. But I'm her biological parent and just now found out that I still had rights to her. The temp guardianship was only till my child's mother turned 18 and she's now 30.