OP:
Do you keep a backup drive of the 2018 MBP?
What do you use as a backup app?
Standard way to do it is to do this:
- take new MBP out of box, put it on table
- connect backup drive
- open lid, new MBP will start automatically
- choose your language and begin setup
- setup assistant will ask if you wish to migrate from old drive.
- YES you want to do this
- "Point the way" to the backup drive
- Give setup assistant time to "digest everything" (takes a little while)
- Setup assistant will present "a checklist" to you of things to migrate
- I suggest you accept "everything" and just let it go
- When the transfer is done, you should see your [old] login screen, just as before.
If you DON'T have a backup, you should be able to connect the two computers via a USBc cable, and setup assistant may work that way.
But the migration will probably go more slowly.