You can make this easier by turning 3 5/6 into a decimal which would be 3.83
Now you can set up a conversion knowing that there are 12 inches per foot:
3.83ft/1 * 12in/1ft <---You must set it up so that the ft will cancel out so the answer would be in inches.
You multiply 3.83 * 12 = 45.96.
Therefore the answer is 45.96 inches.
Hope this help!