Preparing system for MD simulation for polymers built in GaussView 6

GROMACS version: 2020.1
GROMACS modification: Yes/No

Hello!
I have been doing DFT simulations on organic polymers with Gaussian software, and want to do MD simulation in Gromacs for the same polymers. I’m being stuck to prepare the system because the polymers and solvents am using are not the Gromacs database. How could I create topology for polymers built in GaussView 6?
Regards, Thank you in advance