MiPad 4 Update Problem

I unlocked my MiPad a half year ago. The Unlock Password i used is lost an i can not remember.

On the MiPad i have the Xiaomi Rom Version 9.5.9

Now i want to Update the MiPad. I downloaded the newest Rom File as a Zip File. After i choose it the MiPad shows me a message, that the MiPad will restart now and i have to write the unlock Passwort. I don't know it, so i cancelt the update.

What can i do?
How can i get the Password?