This isn't a SQL Developer question. You should close this and ask it in the Database - General forum.
Having said that, the tnsnames entry for newmod needs to be on the server where the source database is running.
Actually, I was not sure where to post this question....
Is there an option to 'close' the discussion?
However, I think the problem is that there is not a service name 'newmod'...
There is a tns names entry called newmod but not a service name.
Can we access this database through a database link based on ip addresses for example?