Loki helm chart upgrade to 3.x with PVC

Hey, I am using Loki via helm chart and want to upgrade to chart version 3. There are major changes and I cannot find a solution for this:
I am using Loki in a k3d cluster and Loki is using a specific persistent volume on a filesystem outside of the k3d cluster.
With helm chart version 2.16.0, i am using the persistence.existingClaim param and its working fine.
How could I still use that persistent volume with chart version 3.x? There is no such option for PVCs or something.
Can anyone help me?