I cant destroy hollow keep outline replace

Every time i try to use /fill and i place space on the last word it recoments me to [ and then to replace outline keep hollow and destroy, but if I put them in, them don,t work why?

Edit: if i put in [ then then they show up. But if i don’t they do not show up. And if i put destroy/hollow/keep/outline/replace without the [ it doesnt work