why are you using embedded mode? Did you try using the remote client first? Here are the docs pages for starting a 3-node cluster in Docker using the remote client.

https://ignite.apache.org/docs/ignite3/latest/quick-start/start-cluster

And the embedded mode docs, if you need to use the extended features of embedded mode in your application.

https://ignite.apache.org/docs/ignite3/latest/quick-start/embedded-mode

I suggest starting with the remote client if you are new to Ignite. It will work even with a single-node cluster.