Simulation of CHARMM-GUI PDB Reader output

GROMACS version: 2024.2
GROMACS modification: No

Hello, I tried to build protein-ligand system with covalent bond using CHARMM-GUI. I used the solution builder but got problem because it can not change the water model (I want to use the TIP4P instead of TIP3). I changed it manually but somehow got more errors.

So I went to PDB Reader in CHARMM-GUI, but I don’t know how to use the output files in GROMACS since the format is for NAMD. Is there any way to read the output files of PDB Reader in GROMACS or convert them to GROMACS-supported format?

Thank you