Deleted Notes

Hello Chiqlu, From what you said "Could not find Deleted Folder", Normally any deleted Notes should be seen in the "Recently Deleted" in you iCloud Folder. Deleted notes are retained for approximately 30 days before they are deleted from from the iCloud Folder. If you are not seeing that then the only other option is do a restore IF you had done a iCloud backup before taking your device to the iPhone Technician.

Restore your iPhone, iPad, or iPod touch from a backup - Apple Support

Hello Chiqlu, You say you backed up iPhone to your computer. Is this computer a Mac computer? If yes, and you sign into this computer with same Apple Id, then check your Mac computer Notes app for the same deleted iPhone Notes. Apple devices sync with each other. If your computer is a Mac and you keep it powered on the Notes may already be deleted, but should still be in the iCloud Notes deleted Folder. If it is your in luck. If your computer is Windows, and you October iTunes backup is too old, then you may be out of luck. Sorry.