So you’re actually convertin from bsp to ase. This means the models are still in there.
To decompile a bsp to a map:
q3map2 -convert -format map -fs_basepath <complete path to your etmain> -game ET <complete path to your bsp>
Note: never use it to copy someone else’s work if you don’t got permission. If you haven’t, decompiling may be even breaking the agreement stated in the readme file of them map.
If you got the .map, open it in Radiant or another .map editor and search around for entities and structures you don’t want in the .ase.