old ipad mini 9.3.6 transfer data to new ipad mini how?

That is what you need to do.

You need to start by backing up your iPad to either Apple's iCloud ( you may need to pay for additional, monthly storage space ) or by connecting your older iPad to a older Mac or Windows PC computer running the latest iTunes or, if a newer Mac with a much newer macOS, use the macOS Finder to do the device backup.

Then restore this data from iCloud or iTunes/macOS Finder to the new iPad.

Make sure your both iPads are, at least, charged to 50% or greater to attempt this.

If NO access to a Mac or Windows computer, you will have to seek help from a good friend or family member to help you out

OR

Search online to locate and call contact your nearest, “local” Apple Store location to try/attempt to make an appointment to get your Apple iPad upgraded/updated to its latest iPadOS 14.6.

Apple Store employees will be glad to help/assist you.

Best of Luck to You!

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