cannot found module 'ng-persian-datepicker'

[nkm96]

Hi. I followed all instructions to install your package but unfortunately I got this error when I add line
import { NgPersianDatepickerModule } from 'ng-persian-datepicker';
in app-modul:
cannot found module 'ng-persian-datepicker'.

Folder "ng-persian-datepicker" is not in node modules folder.
all needed packages was installed successfully.
my angular is up to date.