Samsung S9 Notes

If you're using Samsung Notes, make sure the cloud backup option (to your Samsung Account) is active, otherwise the notes are only stored locally on your phone and any factory reset will automatically wipe out those files with no way to recover them.

Alternatively you can export these to other file formats for manual backup to cloud storage or copying to external storage/PC.
 
I'm looking for a way to transfer my S9 Notes to my Pixel 4 XL coming today. The onlu way I've found is to send them via email in the form of PDFs to myself. I can then open them and copy and paste them into the general Note app of my choice. Unless I am able to download the Samsung Note app on my Pixel.
 
Unfortunately that is correct. You can use the Samsung Notes app in certain Windows 10 computers (Samsung ones) but that's about it. I miss the time when you could sync the notes to Evernote, but that partnership is long gone. Now all you can do when moving to a non-Samsung phone is to manually export all notes and transfer them manually either through a cloud service or data transfer.

That's why, even though the feature set isn't great, I've sticked to using OneNote for note taking now, since it pretty much syncs with everything.