how to unlock my iphone xr?

forgot your passcode?

If you forgot the passcode on your iPhone, or your iPhone is disabled - Apple Support

unlock from a carrier?

How to unlock your iPhone for use with a different carrier - Apple Support

There is no such thing as a "code to unlock".

Only the carrier it's locked to can unlock it. Contact them.

https://support.apple.com/en-us/HT201328

I finish paying my XR iPhone that I’m waiting for the code to unlock is been 3 weeks waiting