notepad plus HD lite

Hello everyone,

It is really emergency for us. My husband was using iphone 7 with lasted ios. today he has iphone X. He was using Notepad Plus HD Lite application on his phone. He backed up his phone via itunes. He accidently deleted the old phone while he was switching off the "find my iphone" application. Now, he restored iphone X, that application is on new phone BUT it is giving warning, "that application does not exist on apple store". he cannot reach his notes now. also, they are so important. please help me 😢 😢