My previous ipad is not turning on at all. How can I transfer the data to my new ipad?

If you have a previous iCloud or Mac or Windows PC iPad data backup to use, you can try this.

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

If you have NO previous iCloud or Mac or Windows PC iPad data backup to use, then there is no other methods other than to continue to try and get that previous iPad working again.

For iPad models with a Home button, do a simple hard reset of your iPad by holding down both the Home and sleep/wake/power button simultaneously until your iPad goes to black and restarts with Apple logo, then release the buttons.

OR

For much newer design iPad models, without a Home button, try the new simple hard reset procedure for the new 2018/2020/2021 iPad Pros, 2020 iPad Air 4 and 2021 iPad Mini 6 models.

1. Press and release the volume up button.

2. Then immediately press and release the volume down button.

3. Then, press and hold the single sleep/wake/power button You will see the Slide to Power off button, but keep on holding down the power button until you see the Apple logo, then let it go.

Once you have performed all the steps, wait for a few seconds and your 2018 iPad Pro will boot up completely to the iPad Pro’s Lock screen.

If no success,

Try other known good, compatible power/charging cables and/or other known good 18 or 20W power/charging adapter blocks to test for current cable and/or power/charging block failures.

Keep everything plugged into the iPad, wait awhile, then try normal start up of the iPad.

If still no joy, re-peform the hard reset procedures, again to try a get your iPad restarted.

If still no joy,

Power/charge cables and/or power/charge adapter blocks can AND DO fail at any time for any reason.

If no spare power/charging cables or power/charging adapter blocks or NO joy on getting this iPad charging, you can purchase new cables and power/charging blocks from your nearest, “local” Apple Store location or from Apple's own Website.

OR

Purchase new, third party Apple MFi ( Made for iOS devices ) certified power/charging cable and adapter block, from online retail, mobile device sellers, to test with, in order to determine that your existing power/charging cables and adapter block is bad/faulty.

OR, if no success with brand new power/charging cables and/or power/charging adapter blocks,

You may need to use the “Get Support” link, at the top far upper right hand corner of every Apple Support Community Webpage, and make an appointment for your nearest, local Apple Store and bring your iPad and charging cable and adapter block, to the appointment, for Apple employees to test/diagnose and options presented to you.

They may be, also, able to get your data off of your old iPad and onto the new one for you.

Best of Luck to You!

Unless you are able to switch-on and successfully enter the iPad Passcode, you’ll not be able to recover any data locally stored on the iPad.

iOS/iPadOS uses and encrypted filesystem; successfully entering the Passcode unlocks the iPad security-chip (the “Secure Enclave”) within which the only copy of the encryption keys that are required to decrypt the locally stored data is stored. If you cannot enter the passcode, you cannot decrypt data.

As is, you are entirely reliant upon having a pre-existing iCloud, iTunes or other backup of your data.