Backup/restore from admin GUI? docker cluster setup question

I’ve been developing code with data on a 3 server cluster for a while and would like to move the data to a docker cluster. My first idea was to take a backup and just read it into the docker cluster but for that, I have to install couchbase on the hardware that runs the docker images to get to the restore binaries. It would be nice to have a GUI interface hook for that?
The restore from the hardware server (5.x) into the docker cluster did not work, I assume because of port/firewall settings.
Next thought was to set up replication between the hardware cluster and the docker cluster (on a different machine).
Replication timed out, again I assume ports that need to be open (which ports?). the demo examples/videos I’ve watched, all are from docker cluster to docker cluster on the same machine so the problem of port setup should not be a problem.
Any insights? or maybe an example would be appreciated. Btw. I think Couchbase is awesome, trying to get it into the build-environment at my current company.

upgraded the hardware cluster to the same version of Couchbase, did a full backup.

When building the 3 server docker cluster, build the node1 server a little different with an extra backup volume which is linked to the backup device from the hardware cluster. Then when the docker cluster is up, attach to the node1 docker image with the ‘docker exec bash’ command and do a cbbackupmgr restore. This is also the way to backup the docker cluster.
I did not have the time to investigate why the replication did not work.