Debian how to install firmware files to operate?

Hi again,
i am working this past years with Linux debian but tried to reinstall it ; this worked fine but after the initial pxe boot, the installation halts with this error: "some of your hardware need non free firmware file to operate.The firmware can be loaded from removable media such as a USB stick or floppy" can your understand the meaning of this error or do you have an answer that i can use immediately to resolve the error?
Thanks for all
Error:
Some of your hardware need non free firmware file to operate.
The firmware can be loaded from removable media such as a USB stick or floppy
