There is no way to check your registered password.
If you forgot your password, follow the steps below to change it.
Note: Be sure to keep a memo of your password so you don’t forget it.
To change your password:
1. Tap More > Settings > Account.
2. Tap Password.
3. Enter your new password two times, then tap OK.
Note: If your device is locked with a passcode or Touch ID, you will have to enter it when you change your password.
For a video guide, see here
Note: If the video doesn't play, try opening the link with a different browser.