On-premise Docker environment to Google Cloud migration

I have a scenario where customer had application and running containers in Docket at on-premise and now they wanted to move docker environment to Google Kuberbernets.

I am clear about setting up container registry and creating clusters in GKE, but looking for the requirements to migrate the docker containers to Google repository and what is the process.

Are the containers stored in an on-prem registry or just locally in docker?

If they are stored in an on-prem registry you may be able to deplicate them to a new target if that is supported. Otherwise you may just have to retag the images and push to the new registry.

What do you mean with containers in docker?

Just a docker file and a docker run? Using any esoteric option?

Or using docker compose? You may want to check kompose in that case.

But, basically, you want to create pods on kubernetes. That might be easy if plain docker containers without esoteric options are used, not so easy in other cases.

There is no algorithm/recipe to follow :+(