Can't find screen time passcode

From the article If you forgot your Screen Time passcode - Apple Support :

How to reset the Screen Time passcode for your child's device

If you’re using Family Sharing to manage a child’s account, passcode reset options won’t be available on their device. Use the following steps on the family organizer's device to reset the Screen Time passcode for your child.

On an iPhone, iPad, or iPod touch

1. Make sure that the family organizer's device is updated to iOS 13.4 or iPadOS 13.4 or later. 
2. On the family organizer's device, go to Settings > Screen Time.
3. Scroll down and choose a child’s name under Family. 
4. Tap Change Screen Time Passcode, then tap Change Screen Time Passcode again. You might be asked to authenticate with Face ID, Touch ID, or your device passcode.
5. Enter a new Screen Time passcode, then enter it again to confirm.

On a Mac

1. Make sure that your Mac is updated to macOS Catalina 10.15.4 or later. 
2. Choose Apple menu  > System Preferences, then click Screen Time.
3. Select a child's name from the drop-down menu in the left sidebar. 
4. Click  Options in the lower-left corner. 
5. Click Change Passcode, then click Forgot Passcode. 
6. Enter the Apple ID and password* that you used to set up the Screen Time passcode.
7. Enter a new Screen Time passcode, then enter it again to confirm. 

If you have Share Across Devices turned on, your new Screen Time passcode will automatically update on those devices after you reset it. 

If you still have issues resetting your Screen Time passcode, contact Apple Support.

*Learn what to do if you forgot your Apple ID or password.