The following steps will help you import your notes from Simplenote easily.
Tools tab in Settings
Export notes to download your notes as a .zip file.
Simplenote from list of apps.
.zip file, go to Notesnook app > Settings > Notesnook Importer and click on “Import from ZIP file” & select the .zip you downloaded earlier.
Simplenote’s export is, well, pretty simple and the Notesnook Importer supports 100% of it. It also preserves all the formatting and indenting in the imported notes.
This can happen in notes for which you have enabled Markdown in Simplenote. Notesnook Importer follows this flag during processing and respects Markdown rules during the conversion to HTML. If you want to preserve the formatting of your notes, it is best that you disable the Markdown formatting for all your notes in Simplenote. This will force the Notesnook Importer to import all your notes as plaintext.