declare
 cursor c2 is
 select * from jobs ;
 begin
 for c2_rec in c2
 loop
 insert into jobs_new(job_id , job_title , min_salary , max_salary)
 values (c2_rec.job_id , c2_rec.job_title , c2_rec.min_salary , c2_rec.max_salary)
 where not exists (select * from jobs_new where jobs_new.job_id = jobs.job_id);
 end loop;
 end;

You can't use a where clause with single row inserts (insert ... values ...).

The good news is: you don't need a cursor at all!

You can do an insert ... select ... instead. Like:

insert into jobs_new (
  job_id,
  job_title,
  min_salary,
  max_salary
) 
select * from jobs
where not exists (
  select *
  from   jobs_new
  where  jobs_new.job_id   = jobs.job_id
);

Not only should this work, it'll be faster than the original cursor loop.

Remember: if you're doing DML (insert/update/delete) inside a loop, you're Doing It Wrong™.

Use one statement to process many rows. Not many executions processing one row!