I can't turn on my iPad because I forgot my iCloud id and password

Welcome to the Apple community.

Unfortunately, unless you know the Apple ID, there is absolutely nothing that can be done, you cannot use your mobile device. You may be able to find your Apple ID at Look up your old and forgotten Apple ID

Unfortunately, you cannot do very much with your phone unless you get assistance from the previous owner, they should either provide you with the password to unlock it or remove their account from the phone entirely remotely through iCloud.com > Find My Phone.

If you aren't able to get assistance from the owner and are unable to get a refund for your purchase, please dispose of the device responsibly by sending it for recycling.

Hello, I can not turn off the mobile phone ICloud problem. dial Id and password to remove your writing Id blocked

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If you are unable to remember your password, security questions, don’t have access to your rescue address or are unable to reset your password for whatever reason, your only option is to contact Apple ID Support, upon speaking to an operator you should explain that your problem is related to your Apple ID, this way you will not be charged for assistance, even if you don’t have an AppleCare plan.

You will need to show patience with the procedure and be prepared to demonstrate without question that the account belongs to you. Don’t expect access to be restored immediately and if you aren’t the owner of the Apple ID registered to the device the account won’t be reset.