Access atlas mongodb from DigitalOcean VPC

Currently, I have a self-hosted MongoDB cluster with the replica sets inside a private VPC on DigitalOcean. All of the applications access the mongo cluster using private IP only. I want to migrate this mongodb cluster to atlas with zero downtime. I can expose my self-hosted mongo cluster over the DNS so will be using mongomirror for migration. But after migration how my applications can access atlas MongoDB cluster? My applications are deployed using kubernetes but how can I find a range of IPs to whitelist?