The only password available to a stock iPad is the one you put so that when you first turn on the iPad, you have to enter a password at the lock screen. It can either be a simple 4-digit number or a mo complicated one. You can set restrictions via the Settings app, but nothing like requiring a password.
That's it for stock, you can't individually lock apps or folders. There are some for jail broken iPads, but not stock. Sorry.
Marilyn