This quick checklist will help you get your Classic Notes into Lightning Experience for a richer experience for your users.
Find the blog post “Pro Tip: Simplify File Management with Salesforce Files in Lightning Experience” here:
https://admin.salesforce.com/pro-tip-simplify-file-management-salesforce-files-lightning-experience
And the companion blog on Enhanced Notes in Lightning Experience here:
https://admin.salesforce.com/pro-tip-boost-note-taking-enhanced-notes-lightning-experience