How to unlock iphone 7plus

Not easily.

If you forgot the passcode, you will need to restore the iPad following these steps: link-> If you forgot the passcode on your iPhone, or your iPhone is disabled - Apple Support

Then if you don't know the Apple ID and password it was signed into, you will need to recover it, before you can access the iPad after restoring:

link-> If you forgot your Apple ID - Apple Support

link-> If you forgot your Apple ID password - Apple Support

Deal with your Apple ID first.

As Tim mentions, recover the Apple ID first. You will need it once the device is restored.