Accidently deleted notes app and now all note are gone?

Hi Sirhye,

Thanks for posting in Apple Support Communities. Your notes are generally associated with an email account; either iCloud or a third-party email. It sounds like your accounts may have been removed or notes was disabled for them. You can check these settings by starting with this guidance from Add or remove accounts in Notes on iPhone - Apple Support.

"Add other accounts

You can use the Notes app to manage your notes in other accounts, such as Microsoft Exchange, Google, and Yahoo.

1. Go to Settings  > Notes > Accounts > Add Account.
2. Do one of the following:

• Choose an account provider, then enter your account information.
• If your account provider isn’t listed, tap Other, tap Add Mail Account, enter your email account information, then turn on Notes for that account."

Take care.