As there is no display on the screen it needs to be replaced.
Here is a link that shows how to do this.
Here is a link that shows suppliers for the part. It is only shown to give you an idea of the cost.
If you find this all too daunting, I suggest that you contact at least 3 reputable, professional. mobile phone repair services and ask for a quote for the repair. I suggested at least 3, as this way you will have a better idea of the cost if all the quotes are nearly the same.
Hopefully this is of some help.