if my old ipad OS version older than 9.00 how to transfer content to new ipad?

The iPad does not need to have the current iOS version.

Use one of the methods shown here other than Quick Start.

Transfer data from your previous iOS or iPadOS device to your new iPhone or iPad - Apple Support

The process to transfer data from old to new iPad is straightforward.

These support pages should get you started with setup of your new iPad - and the methods of transferring your data from old to new iPad:

Set up your iPhone, iPad or iPod touch – Apple Support

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

Use Quick Start to transfer data to a new iPhone, iPad or iPod touch – Apple Support

If the donor iPad, from which you are transferring your data precedes iOS12.4, QuickStart will not be available.

“Transfer” is rather a misnomer. In reality, your data and setup is merely cloned to the new device. Nothing is moved or removed from the original device.

An alternative is to restore either an iCloud or iTunes backup to the new device:

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

Restore your iPhone, iPad, or iPod touch from a backup - Apple Support

Apps are not directly transferred between devices. For Apps, the transfer process creates a record of the Apps that are installed on the donor iPad - and it is this record of installed Apps that is transferred to the target (new) device. For Apps that are still available for download from the App Store, the corresponding Apps are automatically downloaded and installed from the App Store.

If you need assistance, you can make an appointment for the Genius Bar of your local Apple Store or Apple Authorised Service Provider (AASP) here:

Genius Bar Reservation and Apple Support Options - Apple

You can do this via iCloud by going to Settings, then tapping on your profile, then tapping iCloud, then enable it. *Do this step for both devices.*

Important note: If you iCloud Drive, or iCloud Photos exceeds 5 GB (If you are not already using iCloud), you may not be able to transfer content unless if you delete photos and files, or buy iCloud+ for extra space.