sm_03,
Glad to hear back from you!
I understand you are now using an iPhone 6s and you are hoping to gain access to the notes that were on your previous iPhone. I can help.
If you were using iCloud to sync your notes, you should make sure you are signed in to your iPhone 6s using the same Apple ID account under Settings > [your name] > iCloud. Then, make sure you turn on Notes. You can also check on the iCloud website to confirm if you were syncing your notes to your iCloud account.
If you were not using iCloud, it's possible that you had your notes saving to a third-party email account instead. I would recommend making sure you've set up the same email accounts on your iPhone 6s, that you had set up on your iPhone 7. Then, make sure Notes is turned on under Settings > Passwords & Accounts, as discussed under, 'Check your account settings' in this article: If you're missing notes on your iPhone, iPad, or iPod touch - Apple Support.
There is also the option to restore from a backup: Restore your iPhone, iPad, or iPod touch from a backup - Apple Support. Notes that were syncing to iCloud are not included in a backup. However, if notes were not syncing to iCloud, it's possible that they were included in a backup that was performed on your computer via iTunes (or Finder if using macOS Catalina).
Best regards.