First, make sure your system is up-to-date and restarted. This prevents compilation issues later on.

Then, add the contrib section to your apt sources configuration. It should look similar to this:

# deb cdrom:[Debian GNU/Linux 12.5.0 _Bookworm_ - Official amd64 DVD Binary-1 with firmware 20240210-11:28]/ bookworm contrib main non-free-firmware

deb http://deb.debian.org/debian/ bookworm main non-free-firmware contrib
deb-src http://deb.debian.org/debian/ bookworm main non-free-firmware contrib

deb http://security.debian.org/debian-security bookworm-security main non-free-firmware contrib
deb-src http://security.debian.org/debian-security bookworm-security main non-free-firmware contrib

# bookworm-updates, to get updates before a point release is made;
# see https://www.debian.org/doc/manuals/debian-reference/ch02.en.html#_updates_and_backports
deb http://deb.debian.org/debian/ bookworm-updates main non-free-firmware contrib
deb-src http://deb.debian.org/debian/ bookworm-updates main non-free-firmware contrib

Then, add the backports repo, update apt and install the required packages. As root:

codename=$(lsb_release -cs);echo "deb http://deb.debian.org/debian $codename-backports main contrib non-free" | tee -a /etc/apt/sources.list
apt update
apt install linux-headers-amd64
apt install -t stable-backports zfsutils-linux