所有文本框已满后如何显示提交按钮？

I'm making a game with 6 dynamic buttons as "btn" at the top row and other 6 "lamp buttons" on a buttom row. Player clicks on a top row button and text displayed in a bottom row button after clicking on it. As soon as all the lamp buttons are full with text, I want a submit buttom to appear.I'm making a game with 6 dynamic buttons as "bt