i would like to buy a Lightning cable to lightning caple to transfer all from iphone 7 to iphone11 max

It isn't transferred that way. Click on this link to learn how to "Transfer content from your previous iOS device to your new iPhone, iPad, or iPod touch". Select one of the three options: Quickstart, iCloud, or iTunes/Finder. --> https://support.apple.com/HT201269

Since the policy now seems to be not to force people to click on links to read solutions I will copy and paste the link here:

Transfer data from your previous iOS device to your new iPhone, iPad, or iPod touch

Set up your new iOS device from a backup of your previous iPhone, iPad, or iPod touch.

Before you begin

• If you have an Apple Watch and you got a new iPhone, unpair your Apple Watch from your previous iPhone before you set up your new device. Unpairing automatically backs up your Apple Watch so you can restore it after you pair with a new iPhone. 
• Make sure that you have a backup of your device.
• Have your Apple ID and password ready.
• Transfer your SIM card. If your new device needs a different SIM card than what you have, or an eSIM, contact your carrier.

Select a method

Next, select one of these transfer methods.

Quick Start: Use your iPhone or iPad that's already running iOS 11 or later to automatically set up a new device.

iCloud: Transfer your data and purchased content to your new device from your previous device's iCloud backup.

iTunes or Finder: Transfer your data and purchased content to your new device from a backup you made with iTunes or Finder.

you can't do that

Because that is how Apple has designed it to work, probably in the interest of security. Anyway, you have your "solution", if not the one you wanted.