iPhone 6s plus screen broken problem

First of all check that the phone itself still works, a popular method is to plug it in to a computer and listen for any tones, or call it from another phone. If it still works then all that is needed is a screen replacement.

Buy a new screen from here:

This is the screen by itself

[produto vinculado ausente ou desativado: IF315-000]

This is the screen plus the tools you'll need to do the repair

[produto vinculado ausente ou desativado: IF315-033-7]

And this is the guide you'll need to follow in order to replace the part.

Substituição do conjunto do display do iPhone 6s Plus

Let me know if this fixes your issue.