My daughter made an adult Apple ID and i don’t know the password

You can see if you can convince Apple that you are indeed the parent of this child. You have multiple hurdles you have to deal with in this because Apple is pretty strict about privacy and account security. You have to convince them that this account should indeed be a child account and that you should be in charge of it. Also that you aren't some person off the Internet who is trying to pull a practical joke on somebody or trying to take control of their account. Look at it from what could be Apple's perspective.

Contact Apple for help with Apple ID account security - https://support.apple.com/HT204169 "This article provides country-specific Apple Support contact information for customers seeking help with their Apple ID password or other security-related issues."

See if you can convince her to let you do it. You do have ultimate control of her phone.

Click on the link to read how to 'Update the birth date associated with your Apple ID' - https://support.apple.com/HT204164