My condolences on your loss.
Sounds like you were given only the hard drive and now want to create a Proxmox server using those backups?
If yes, then the first step is installing Proxmox. Then configure storage locations. Then copy the backups to those locations.
If no and you want only to extract the backups, the lz extension indicates the backups were compressed using lzma. Loosely, that is a compression algorithm similar to zip, gzip, or tar.
The qemu portion of the file name indicates the backups are of a qemu/kvm system. Proxmox supports 1) Linux LXC containers that fundamentally are processes and 2) qemu/kvm virtual machines. The latter is similar to Virtualbox, which is a popular virtualization technology for desktop systems. A virtual machine is a full self-contained system running on top of another system. Conversely, a container is basically an isolated process.
For a new Proxmox user, the web browser interface likely is the easiest way to restore backups. Some places to start learning:
Proxmox Wiki:
https://pve.proxmox.com/wiki/Main_Page
Proxmox admin manual:
https://pve.proxmox.com/pve-docs/
If you are creating a new Proxmox system, look for hardware that supports virtualization. A beefy CPU with virtualization extensions, lots of RAM, fast hard drives. With many virtual systems many people use multiple socket CPUs with multiple cores. If you have only a few virtual systems and they are not high demand, a single 4-core CPU might get by. For example, on my home desktop I use a 4-core i5 CPU and 16 GB of RAM. I run a couple of concurrent virtual systems as well as the host system. At work I use mostly refurbished Dell R710 systems, with dual Xeon CPUs and anywhere from 16 to 72 GB of RAM with SAS hard drives.
I hope that helps.
