‘mat-card’ is not a known element in Angular 7

I can not see your EmployeesComponent in your list of declarations. The EmployeesComponent need to be declared in the same module as where you import the MatCardModule, like:

declarations: [
    EmployeesComponent
],
imports: [
    MatCardModule
]

I am guessing either that you have forgotten to declare the EmployeesComponent in your app module, or that you have another module, perhaps Employees module, where you have to import the MatCardModule.

You can import MatCardModule as

import { MatCardModule } from '@angular/material/card';