Apple provides notoriously limited export options for Apple Notes. The only officially supported option is to export
  each note one-by-one as a PDF file.
Luckily, there are third-party tools that make this process much easier.
To import your notes from Apple Notes:
  - 
    Download Exporter 
    from the Mac App Store.
  
- Follow the app's instructions to convert your Apple Notes into plain text files.
- 
    Return to the Standard Notes application, and open the Account menu at the bottom left of the interface, then choose Import.
  
- 
    Click and drag your files to the empty box provided for auto-detection, and click on Import to proceed. You may also click or tap on the box to open your device's file picker and select the files for import