how do i recover a screen time password

If you are trying to wipe a device to be sold, then you need to clear the device, What to do before you sell, give away, or trade in your iPhone, iPad, or iPod touch - Apple Support

However, if that will not allow you to do that, you need to put the device into Recovery Mode if you cannot remember the Screen Time passcode. See Recovery mode here, If you forgot the passcode for your iPhone, iPad, or iPod touch, or your device is disabled - Apple Support

Forgot (You need a computer to follow these steps. If you don't have a computer, borrow one from a friend,)

I am sorry, if you have forgotten your Lock Screen passcode and there is no backup, then all data is lost, if you have one, not to worry. But if you have forgotten the Screen Time Passcode and even if you have a backup everything is lost because restoring will bring back the screen time restrictions (Status Quo).

What you will get back is what you have synced to iCloud and uploaded to iCloud Drive; information already synced and stored in iCloud, like Contacts, Calendars, Bookmarks, Mail, Notes, Voice Memos, shared photos, iCloud Photos *, Health data, call history, and files you store in iCloud Drive.

*-If you had turned on iCloud Photos, your content is automatically stored in iCloud. 

Forgot either? Click below…

Click->If you forgot the passcode for your iPhone, iPad, or iPod touch, or your ...