could not back up the iPad because an error occurred while reading from or writing to the iPad

Hi MollyChil, thank you for posting in Apple Support Communities.

Please find the following linked article that may help you resolve your issue:

https://support.apple.com/en-us/HT203271

If the issue is not resolved by the above support articles and suggestions, you can make an appointment and have your iPad inspected at an Apple Store or AASP (Apple Authorized Service Provider). Please use this link to find one in your Country Apple – Location Selector. After going through the process, you will be given all the options available.

You can also contact Apple Support as follows:

• Online:--> Genius Bar Reservation and Apple Support Options - Apple;
• Contacting a local Apple Store or AASP among the list provided above but also again as follows Apple – Location Selector; or
• Using the "Apple Support" app, available and downloadable from App Store.