How do I delete iMessages app from my iPad

You can inhibit syncing of SMS/MMs Messages from your iPhone to iPad by changing a few settings on your iPhone:

On your iPhone:

Settings > Messages > Text Message Forwarding - set to OFF - and explicitly disable your iPad from the list of devices.

Settings > Messages > MMS Messaging - set to OFF

Also ensure that Messages in iCloud is disabled on both your iPhone and iPad:

Settings > [Your Name / AppleID] > Messages - set to OFF

Also on iPad, sign-out and disable Messages

Settings > Messages > Send & Receive > AppleID - tap, then select Sign Out

Settings > Messages > Messages - set to OFF

More information:

How to forward SMS/MMS text messages from your iPhone to your iPad, iPod touch or Mac - Apple Support

I hope this information and guidance proves to be helpful in resolving your issue.

The Messages app is included as part of iPadOS and cannot be deleted. You may hide it in a folder if you wish.

You may also restrict access to it this way:

Use Guided Access with iPhone, iPad, and iPod touch - Apple Support