Starting a REMD run

GROMACS version:2023
GROMACS modification: No
I have manually created a series of 16 .tpr files corresponding to 16 temperatures named IV_0.tpr to IV_15.tpr. I am trying to start a short simulation to test the acceptance ratios.

My machine is running: CPU: Intel Xeon Silver 4110 (32) processors

I have tried (based upon web searches)

gmx mdrun -s IV_.tpr -multi 16 -replex 1000 -noappend
which returns: filename IV_.tpr does not exist

gmx mdrun -deffnm IV -multi 16 -replex 1000 -noappend
which returns: unknown option -multi

gmx mdrun --deffnm -np 32 -replex 1000 -noappend
which returns: unknown option -np

gmx mpirun -deffnm -np 32 -replex 1000 -noappend
which returns: mpirun is not a GROMACS command

What is a viable mdrun command to start a remd simulation in this case?

Best,

Ken