Trying to add old iPhone 8plus back into my iOS trusted devices using my current 11pro

I had an 8plus that was held/taken from me a few years back in a vehicle accident. Which was total bs. However, I got a new 11pro during that time and am still using it to this current day.

I just recently received my 8plus back, now that my traffic incident has been closed and resolved. The issue at hand is, the phone is in airplane mode. And has my old passcode protection on it, which I do not remember what it was anymore.

I don’t have it as a trusted device anymore either, so I can’t simply type in a verification code from my 11pro enabling me to gain access and change the passcode. Please help here?