linuxcnc mint 2.8 to upgrade 2.9

hii,i have a 7i93 mesa cards but we did not install 2.9 linuxcnc.on install machine mesa cards we dont see the ethernet cards.
i bought new computer we can not install devian version we did install linux mint versiyon than install linuxcnc so at the moment we dont see the cards.
is it possible to explain what we are doing .

Br.

What are the computers Make and Model?
Mint is now using a very old kernel version (5.4)
Debian Bullseye is on 5.10 and the Debian unstable branch where the Linuxcnc currently lives is on 5.16.
I suspect your network cards are not supported in kernel 5.4.
eg. The NIC in my PC was not supported until kernel 5.9.

Also, I like to use Debian Bullseye because it does not have Python 2 in it and I got in a mess with earlier versions
So I think you have three choices
1. Find the driver and install it after you get linux installed but Debian makes it hard to install the OS without network. 
2. Install debian bullseye and compile linuxcnc from source (There are good instructions to do this on the QTPYVCP web site. Be sure to install from the non-free ISO to maximise driver support.
3. Install Debian Bullseye, upgrade to their unstable branch by following the instructions on the Debian site and then install linuxcnc by typing:
sudo apt install linuxcnc-uspace
This will bring in the preempt_rt kernel

I've done all 3 of these and I think option 3 is the easiest but Option 2 is not much harder and lets you keep much more current as you can upgrade to the latest in master branch with about 3 commands in the terminal