Migrating over your local network has a high failure rate. It is always best to migrate from your old Mac’s Time Machine backup during the setup of the new Mac.
If you migrated after setting up the new Mac. Then you now have two user accounts on the new Mac. That is, providing that the migration actually worked correctly.
If you can not find or log into the old Mac’s account on the new Mac? Then I suggest starting over from scratch. Erase the new Mac, Reinstalling macOS on the New Mac and then Migrating from your old Mac’s Time Machine backup.