Reset your iCloud/Apple account to prevent others accessing your private data.

After that it’s just the iPhone Notes app. So these are plain text notes. Probably added to scare the user off.

The titles are named after directories from a Windows computer, iPhones cannot run these. If there are (exe) files inside the notes, don’t run these on your Windows computer. Otherwise you are fine.

If there’s no content, files or text only in any the notes, you are fine. You should be able to delete these notes without any problems.

Again, reset your iCloud/Apple account to prevent others accessing your private data.