OK, this should be easy...... I would turn it over...I can see where there is a hole on the "top" letting in sunlight. Make that the bottom.....the hinges would then be on the top. Where the drawer used to be....get a small piece of hardware cloth...and secure it tightly. This will be good for ventilation. However....if it gets cold there in the winter...you might want to come up with something to cover that "drawer opening" Scrap wood would work great.
I would definately put a piece of hardware cloth over the hole, ( that is in the top of it now)
Put a latch on the door...so you can secure them in at night. Then get 4 cynder blocks, and make a foundation. This will keep it from getting wet in the rain, and gove the silkies something to hide under if scared...or just to get shade. Looks like this might just work out. Oh, if you do put it up on blocks...make sure they have a small ramp..to get into it. Maybe about a foot from the back...secure a roost. Have fun, be creative...and show us when you are done!!