My Apple watch broke down

I changed my phone, I had an iphone6 and it was connected to the apple watch, and then i bought 11pro max and to connect my watch to it i reseted my watch.

when it opened it asked me to enter my very old email password which i don’t know its password.

The old mail is ****@****.com

I have my apple watch box

i got some infos from i wish they can help:

MTUW2LL/A / AppleWatch Series 4

IMEI ****

(S) Serial No. FH****DT8

[Edited by Moderator]