If you don’t have a pre-existing backup, you’ll not be able to restore your data.
Your iPad uses an encrypted filesystem. Unless you are able to successfully power-on your iPad such that it is running normally - and you are able to enter your passcode - all locally stored data will remain encrypted and beyond reach/unrecoverable.
If you value your data, it is essential that you always keep a backup - this being true for any computer system, not just your iPad. For Apple devices, keeping a backup is relatively painless; you can natively backup your data using iCloud (this process being entirely automatic) or using iTunes:
How to back up your iPhone, iPad, and iPod touch - Apple Support
With a backup, should disaster strike, you can easily restore your data from the backup:
Restore your iPhone, iPad, or iPod touch from a backup - Apple Support