Exporting into GTKRadiant

I’m trying to get a map that I’ve made and put it into GTKRadiant but GTK only takes .map and .xmap files. Unreal doesn’t let me export a level as one of those and when I googled how to change the .fbx into a .map I found nothing helpful. If anyone knows how to do this or somewhere that shows me how to do this that’d be great. It would also save me from rebuilding the entire map all over again in GTK.