Hello and welcome to Apple Support Communities LookinForGuidance,
Thank you for contacting us. We know losing notes is never an easy position to be in, and we want to be as helpful as possible. We can understand why you’d reach out for a solution. To start, make sure you have the most current operating system on your device. (Settings > General > Software Update) Check your account settings (Settings > Mail > Accounts > Notes) The missing notes may be stored with a third-party account or email service, like Gmail or Yahoo. There is also the option to store notes, "On My iPhone", so you want to check your default setting as well. Going into an Apple Retail Store right now may not be an option due to Covid, but you are always able to contact the online support by following this link: Get Support.
Use Notes on your iPhone, iPad, and iPod touch
If you're missing notes on your iPhone, iPad, or iPod touch
If you need further assistance after following the links above, please don't hesitate to reach out, we are always happy to help.
Thank you for contacting Apple Support Communities.
Best regards.