Why can't mongomirror initiate connection to the destination source? [server selection timeout]

[Ramachandra_Tummala]

Is your target an Atlas cluster?
Check below thread
The mongosh connection you have shown is connecting to only one node
What about connection to replicaset?
What does rs.status() show?

Approach to migrate mongodb using mongomirror using 2 GCE only

Welcome to the MongoDB Developer Community Forums @Mohammed_Sahil ! mongomirror is a tool for migrating an existing replica set to a MongoDB Atlas replica set so it has some assumptions about the destination (for example, that this will be a replica set). I recommend using mongomirror if your destination is an Altas cluster, but for migrating to (or from) a more general destination I suggest using MongoPush. Regards, Stennie