Gitlab-ci and nexus

What files are needed to push or pull from gitlab ci to nexus?
I set it like this in .gitlab-ci.yml but it doesn’t seem to find my nexus


error pushing image “” to “docker://”: trying to reuse blob sha256:735956b91a18480450076b4e4a1f403cfe0c0f1dc7bf065341c2446fa045347d at destination: pinging container registry invalid status code from registry 400 (Bad Request)