How do I copy a schema for an instance of Oracle running in a Docker container? Pursuant to this question: 
Is this package missing and if so, how do I fix?

...now I actually want to perform the copy of a schema using this package. ...except I can't figure out how to do that. I've seen this: How to create copy of full schema on same database in oracle but I can't seem to execute the commands. As mentioned in the previous question, we are running Oracle in a docker container, so this might be complicating matters. Again, I'm using DataGrip to connect. Since it's in a container, all of our connections are from remote. ...am I going to have to get into the container somehow? Docker is also something that is outside of my expertise.

I've tried executing: 

expdp fromUser/fromPword schemas=sourceSchema directory=DUMPDIR dumpfile=dump.dmp logfile=explog.txt


...as well as...

exec expdp fromUser/fromPword schemas=sourceSchema directory=DUMPDIR dumpfile=dump.dmp logfile=explog.txt


I've also created the directory object DUMPDIR and granted read/write to it.
expdp is a command line utility that interacts with the DBMS_DATAPUMP API. You run it on the host OS, not from within another client.

https://docs.oracle.com/cd/B19306_01/appdev.102/b14258/d_datpmp.htm#BABHBEHH


  See Also:
  Oracle Database Utilities for more information on the concepts behind the DBMS_DATAPUMP API, how it works, and how it is implemented in the Data Pump Export and Import utilities


https://docs.oracle.com/cd/B19306_01/server.102/b14215/dp_overview.htm#i1009203