Recently bought new iPhone and notes were not transferred. Trying to find old files via Time Machine
As you would know, Time Machine backs up what's on your Mac. Because of this, it's not possible for your Time Machine backups to have copies of your iPhone notes unless you:


also backed up your old iPhone via iTunes on your MacBook, and/or
did have all your iPhone notes backed up to iCloud at some point in time


Scenario 1

This is a more difficult scenario to work with since all you want to recover is your Notes data.  It's not impossible, but to make it practical you would still need access to your old iPhone or use specialised data recovery software. If Scenario 2 applies, try that first. Otherwise, if you do still have access to your old iPhone then you could restore your old iPhone from an older iTunes Backup (located within your TM backups) and then access your old notes that way to either resync back to iCloud or to just copy from and paste into another app (e.g. Pages, Word, Evernote, etc) and then copy from their into new notes in iCloud or your iPhone 7.

Scenario 2

Your Notes data is stored in a Core Data database located in your user Library.  More specifically, it is located in the following path:

~/Library/Containers/com.apple.Notes/Data/Library/Notes

Therefore, within your Time Machine backups you would be looking for the above location to recover your notes from.

Notes: 


The ~ indicates your User directory, not the root level of your drive.
Depending on your situation you may not see this directory by browsing your TM backups. If you don't know how to make this visible there are questions here on Stack Exchange that deal with this.
Within the Notes folder there will be files named as follows:  NotesVx.storedata-yyy where the x could be a 1 or 2 or 3 etc (depending on your version of Notes) and yyy denotes additional file name characters (e.g. shm, etc).


IMPORTANT - This is a database so you can't restore a single note - it's all or nothing! You could restore the whole database, but if you're syncing with iCloud, there is the chance that even if you restore it, that it will sync and then get deleted again.

Another option

You could also just copy the NotesVx.storedata file and edit the file extension by changing it to .html and then open that in Safari. By doing this you should be able to see all your old notes (assuming they were there to begin with). Then it's just a process of copying and pasting into new notes.