I got an idea for an app. Budget 100k. What to do?

I have a cool idea for an app in my head. I'd like to get it made then put in on google play. My budget is 100k.

How can i go about doing this? I heard there is app companies that will build this app for you. Ive been making screenshot of how the app would look like.

Where can i find companies that can do this.