Do you mean that shows you the password of a wifi you are trying to get into or a wifi you have connected to before? There are plenty of ways for the latter but for the first one you could target wifi's that have wps on, those are the easiest to get into and a lot of apps can do the trick for you or if you have a little knowledge about kali linux and it's tools just use the aircrack suite, you can find a lot of tutorials about it on youtube, but for wifi's that do not have wps on it might be a little hard for you without having any prior knowledge.