How to enable micro-k8s add-ons on the target machine which has no internet at all? Please guide.
This depends on the addon. In general addons reach out to public repositories to get yaml manifests, container images, binaries and binaries. For container images you will need a local registry and proper manifests pointing to it. For binaries the best option is to have some proxy.
It may not always be convenient to mirror all resources an addon needs. In such cases you may want to look at offline deployment options the upstream component offers.