Open the Photos app
Tap Albums
Scroll down to Utilities
Tap Hidden
Tap Select
Select the photos or videos you want to unhide
Tap the More button
Tap Unhide
Open Settings
Tap Photos
Turn off Show Hidden Album
If you use the Files app, open Files
Find the folder you want to hide
Move it to a secure location or delete it if no longer needed
Use a third-party app with a passcode or Face ID lock if you need folder privacy