How to transfer Mac Yosemite Notes to Mac Sierra
Why not just sync your notes using iCloud? 

If they aren’t currently associated with your iCloud account, just copy them over to that account (within the Notes app) on the machine running Yosemite. Then, enable iCloud on the machine running Sierra, checkmark “Notes” to sync under iCloud preferences, and then you’ve successfully transferred them. 

It’s a much easier solution than navigating through the filesystem and manually selecting the data.