Ipad i0s 9.3.4

Presumably you are trying to change the email address that is used to identify your AppleID account (i.e., your AppleID username) - and not to create an entirely new AppleID account.

Change your Apple ID - Apple Support

Change your Apple ID password - Apple Support

What to do after you change your Apple ID or password - Apple Support

Updating your AppleID credentials will not impact your locally stored data - or any data that is present in, or backed-up to, iCloud.

However, if you value your data or photos, it is recommended that you always have a backup of your important or irreplaceable data - as doing so safeguards against unforeseen failures or user-error. iOS/iPadOS provide simple methods to backup to iCloud or iTunes:

How to back up your iPhone, iPad, and iPod touch - Apple Support

To be sure of your question:

-you have an iPad at IPadOS version 9 or you have an IPad 9 (meaning 9th generation/2021 model year)?

-you want to change the AppleID for your iPad?

Read this from the the tech site iMore. It explains what will and will not happen when changing to a new AppleID(you do not lose photos on the iPad). However, this is explaining steps for a recent iPadOS. If you are still on iPadOS 9, you are very far out of date and should consider remedying that as soon as possible.

https://www.imore.com/how-change-apple-id-your-iphone-or-ipad