here's mine, 2x4x2ft high. I like having it on legs as the poo goes right through the hardware cloth that's on the bottom into a pan with newspaper, then it gets tossed. last winter I covered it with insulation and had the chicks in the unheated garage when they feathered out, no heat.
after mine feathered out I didn't keep a heat lamp on them. They stayed in the brooder in my garage until I took them to my barn. Between christmas and new years I build a coop outside, and at about 12 weeks they went in it. No heat or insulation, and they seemed to enjoy it. As I opened the pop...
the cage in your post is plenty big enough. What I would do is put it on its back and add some legs to it and put a pan or paper on the floor under it to collect poo.The dimentions of mine are 2x2x4. get some pine shavings to put in the pan or cut down a cardboard box to collect the poo.
here's a pic of my chicks at 1 day they are in a 10 gallon aquarium
this pic is the same birds at 8 weeks
I don't have any pic of them today but they are quite large.
I don't have any right now but I used that cage for my last hatch and kept 12 in it until they outgrew it. You may want to start building something bigger as they grow so fast as you will find out.