Converting Behavioral to Gate Level

If you are using the Quartus native simulator, just run a timing simulation instead of a functional simulation.

If you are using a third-party simulator, you can start with Quartus on-line help.

On the help Contents tab, go to "Integrating Other EDA Tools --> Specifying EDA Tool Settings". This page tells you how to generate the .vho or .vo gate-level netlist with Quartus.

On the help Contents tab, go to "Integrating Other EDA Tools --> Using Other EDA Simulation Tools --> About Using the <third-party> Software with the Quartus II Software --> Performing a Timing Simulation with the <third party> Software".