Once you have SSHed into your Proxmox:
There, you should find two files,
To make sure that you don't pull anything off the enterprise version, comment out the text in
pve-no-subscription.list make sure that you have the following line:
deb https://download.proxmox.com/debian/pve buster pve-no-subscription
Save and exit the file.
Also, just to make sure that we are on the same page, if you check
../sources.list you should have three urls. There you should see:
buster main contrib
buster-updates main contirb
buster/updates main contrib
Try running :
apt update && apt dist-upgrade
After that ends, you will need to reboot. However, in order to reboot, make sure that there are no virtual machines running.
And, when it boots up, you should have Proxmox 6.2