Hey yoganini,
We understand your iPhone is either no longer powering on or its data was erased after updating.
If your iPhone is dead and no longer powering on, we'd suggest forcing a restart of your iPhone SE by doing the following: Press and hold both the Top (or Side) button and the Volume Down buttons until you see the Apple logo.
Afterward, charge your iPhone for at least 1 hour. If you continue to have issues then we'd recommend completing the steps in the "If your device turns on but gets stuck during start-up" section here:
If your iPhone, iPad or iPod touch won't turn on or is frozen
If you're missing any data after regaining access to your iPhone, you can restore a backup using these steps:
Restore your iPhone, iPad, or iPod touch from a backup
We hope this information helps out!
Take care.