You can use the pct command on the Proxmox VE host to copy files between LXC containers and your Proxmox VE host.
Copying a File from LXC Container to Proxmox Host
To copy a file /root/gitea.tar.gz from the LXC container ID 203 to your Proxmox VE host and put it in the path /root/gitea-backup.tar.gz of your Proxmox VE host, run the following command:
# pct pull 203 /root/gitea.tar.gz /root/gitea-backup.tar.gz
The file should be copied to the Proxmox VE host.
root@pve-host:~# ls -lh
total 27M
-rw-r--r-- 1 root root 14M Sep 11 11:54 gitea-backup.tar.gz
-rw-r--r-- 1 root root 14M Sep 11 11:38 gitea.tar.gz