I just need a way to use this mod on a server. when i try to use it, it says change permission query

You just need to install it on your client. The message "You do not have permission to use the World Handler" pops up if the mods detects that you do not have enough permissions (i.e. you are not an operator) on this server to use command. You can disable that check in the config file. It is located in .minecraft/config/worldhandler/worldhandler.toml. In that file you would need to change permission_query = true to permission_query = false. Alternatively you can install configured to change the settings ingame.

tysm, i will see if it works asap

is there a way to use this if i am not an admin?

As i said this disables the permission check and you can use the gui. You will be able to send the commands but they may not have any effect if you dont have the required permissions.