copy files from one ipad to a laptop

If the iPad is working, see:

Use iTunes to sync your iPhone, iPad, or iPod with your computer - Apple Support

Sync content between your Mac and iPhone, iPad, or iPod touch - Apple Support

If your iPad won't start up, then no, there won't be any way to get files from it.

Regards.

While keeping the iPad connected to its Power Adapter, copy any files that you wish to make accessible to iCloud; you may find that some (if not all) the files of interest are already synchronised with iCloud file storage.

From any computer, you can access iCloud storage using a web browser:

https://icloud.com

Simply sign-in to iCloud with the same AppleID/Apple Account. Once signed-in you can copy files to/from the computer.

Manage your iCloud storage - Apple Support

Then unless your partner has a backup of those files somewhere, absent having the battery replaced and hoping those files are still intact there's nothing to be done.

Regards.