Hi,
you maybe want to have a look on: Retrieve kubeconfig from RKE or Rancher 2 custom cluster controlplane node for RKE v0.2.x+ and Rancher v2.2.x+ · GitHub
and then go along: Upgrades | RKE1
Additionally also: Lost rancher-cluster.yml for RKE - #2 by mattmattox can be helpful.