iPhone 6 not working, how do I transfer data to new iPhone SE?

If you have been making regular iCloud backups or backups to your computer, then restore from that backup.

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

Otherwise there is not much else you can do.

Try to attach your phone to iTunes first if successful make a backup but if your phone is totally dead. You need to connect to apple hardware support.

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

mhenes Said:

"How do I transfer Data from iPhone 6 (not working) to new SE?"

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Make Use of Quick Start:

You can transfer this from your old iPhone to your new iPhone using Quick Start: Use Quick Start to Transfer Data to a New iPhone, iPad, or iPod touch - Apple Support