Google script to change the contents of a cell to a checked checkbox if the cell is "TRUE"

Beginner here. I have a google sheet in which rows L, M, and N can contain the following things: "TRUE", "FALSE", blank, something else. I would like to write a script that looks at rows L, M, and N, if the value in a cell is TRUE, it inserts a checked checkbox, and if the value in a cell is false, it inserts an unchecked checkbox. Thanks in advance for any tips!