How to deal with docker containers?

I have inherited some cloud hosted vms, with several services hosted in docker containers on these. Think we server and then DB, both hosted in separate containers. Several (overpriced) vms are involved. Would really like some pointers as to how I can get into these / edit them. Would really like to consolidate. I use proxmox at home and am comfortable in Linux but this is new to me. Any docs / tutorials would be super helpful. Still don't really understand why the design was done quite like this, so if you have insight on that, please let me know why you would do it this way. Thanks!