I can't update my games because it keeps going back to my old apple ID which I am not using anymore

you would have to see if you can get a roll back version check the app developers website

If your apps were from the apple AppStore they should be in the cloud and you should be able to retrieve them on your new Apple device as long as you know your Apple ID and password along with your iCloud password

go to your iCould check email address then you can sign in your email to change it

Sign in to your Apple ID account using your old password and go to my Apple ID and change it there!

- most probably those apps which popup now where downloaded before with another Apple ID
- you need to delete them and download again with the new Apple ID... Some iOS Users Reporting Apple ID Error Messages When Updating Apps

If your wanting to factory reset it to nothing go to settings and general at the bottom you will see Reset click that and then erase all content and settings. You will receive a prompt warning you press erase and it will be back to default like you never used it.

If you just want to reset ur apple id password:

1. Go to My Apple ID (appleid.apple.com).
2. Click "Manage your Apple ID" and sign in.
3. If you have two-step verification turned on, you'll be asked to send a verification code to the trusted device associated with your Apple ID. If you're unable to receive messages at your trusted device, follow the guidelines for what to do if you can't sign in with two-step verification.
4. Click "Password and Security".
5. In the "Choose a new password" section, click Change Password.
6. Enter your old password, then enter a new password and confirm the new password. Click Save when done.

I'm assuming you have already used iForgot etc to reset your password first or that you no longer have that email..
Go to settings, scroll down to itunes /App store.
Click on your apple ID. and you will get some options such as IForgot to send a new password etc. If you truly cannot get your password, then click Signout. Then you will be able to create a new one when you try to register, you may need to create a new email account if your apple id was linked to your old one. Your old apps that will not update, you can delete them by holding your finger on them till they wiggle and click the X. then redownload with your new ID. Hope this helps.

You ALWAYS select an Apple ID of your own choise. This is not done automatically. But, if perhaps someone else did this for you, you can try to recover the password, and if that is no option, just create a new Apple ID on the Apple website, and change it on the iPad