Welcome to Justanswer.com, my name is ***** ***** I will do my best to assist you.
To start with, do you have access to a mac or a pc?
And if so, have you recently connected your ipad to that mac or pc, even if just to charge?
Ok, have you used your mac or pc and went to this link to try and set a new password ***** your icloud / apple id ?
If you set a new password ***** your apple id using that link.. You should then be able to sign in on your ipad using that link.
Try that, and let me know if it accepts the new password. ( and also, make sure when you turn on your ipad that the wireless icon is lit up showing its connected to your network, or else it wont accept the password )
If it still wont accept the new password ***** you set it above, let me know exactly what it says or shows on screen.