Force fields

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I have created my pdb with lipids triglycerides using CHARMM gui , now I run pdb2gmx using gromacs selecting CHARMM forcefeilds, However I get the error "Problem with chain definition, or missing terminal residues. This chain does not appear to contain a recognized chain molecule. If this is incorrect, you can edit residuetypes.dat to modify the behavior.
8 out of 8 lines of specbond.dat converted successfully

Program: gmx pdb2gmx, version 2021.1
Source file: src/gromacs/gmxpreprocess/resall.cpp (line 597)

Fatal error:
Residue ‘OOOT’ not found in residue topology database"

I want to know how can I set up my simulations for lipids or I got a toppar folder from CHARMM gui, when I created the structure, can I somehow tell the pdb2gmx commands to take the force fields parameters from there, if yes how. I am new to using gromacs, and MD simulation in general, would be grateful for any help. Thanks!