Migrate content of Notes App from 10.11 machine to new 10.13 machine
iCloud is likely your best bet, but it doesn't have to be a permanent decison.

First, you can restrict iCloud to just Notes if you like in System Preferences > iCloud preferences. Simply unselect everything in iCloud other than Notes. In this case there is no work on your part other than signing in. The notes will simply move to your Notes app.

When you get your Notes as desired, you can sign out of iCloud after the Notes appear. Go back to iCloud in System Preferences, and sign out. It will ask if you wish to keep everything on your Mac, in which case you should say 'yes'. Of course, you will no longer sync Notes between your devices, but it sounds as if you do not need that feature.