i have a MILP with ~3000 binaries, 300000 continuous variables and ~1MM constraints. I am trying to solve this on the VM how long could it potentially take on a 16 core 128 gig machine? also what are the general limits of creating problems using  pulp that cplex solver can handle on such a machine? any insights would be appreciated
It is impossible to answer either question sensibly. There are some problems with only a few thousand variables that are still unsolved 'hard' problems and others with millions of variables that can be solved quite easily. Solution time depends hugely on the structure and numerical details of your problem and many other non-trivial factors.
scaling MILP using pulp and cplex