Open the Play Store app
Tap your profile icon
Go to Settings
Open Family
Tap Parental controls
Turn on Parental controls
Set a PIN
Choose app and content restrictions
Use a screen lock or app lock feature on your device
Install a trusted app-lock app if your phone supports it
Lock the Settings app as well to prevent changes
Use a child profile or restricted profile if available on your device
Disable Play Store access for the user account if needed