I changed my passcode and my device does not accept it.

If you forgot the passcode for your iPhone, iPad, or iPod touch, or your device is disabled, you'll have to put it in Recovery Mode and Restore it as new while connected to your computer. 

https://support.apple.com/en-us/HT204306

You will have to follow these instructions—>If you forgot the passcode for your iPhone, iPad, or iPod touch, or your device is disabled - Apple Support