Getting old iPad ready to send for repair.

I have a new iPad. Data is transferred and on cloud. How do I set my old iPad back to factory settings before I send it?

Get your iPhone, iPad, or iPod touch ready for service - Apple Support

Part of that should be signing out of iCloud on the device which means the device will no longer sync with other devices using your Apple ID. Deleting data therefore won't be conducted on other devices too.

Sign out of iCloud on your iPhone, iPad, iPod touch, Apple TV, or Mac - Apple Support

Davidclarinet Said:

"Getting old iPad ready to send for repair."

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Q1. "I have a new iPad. Data is transferred and on cloud. How do I set my old iPad back to factory settings before I send it?"

A1. Do as instructed here: What to do Before you Sell, Give Away, or Trade in your iPhone, iPad, or iPod touch - Apple Support

Q2. "If I erase data on old iPad, how can I make sure it won’t affect data in cloud or new iPad?"

A2. Log out of iCloud on this iPad. Being no longer associated to your iCloud account, nothing will sync and it will not affect your other devices, including this new iPad.

The first just resets your settings and leaves data on the phone. For privacy reasons you should erase all content.