Actually there are no magic numbers for space requirements that cover all of us. We keep them in so many different conditions and climates, with different flock make-ups, using different management techniques, and for such different goals that no one number can possibly cover us all. It’s also not that important if the space is in the coop, run, coop and run, or some other way. What is important is how much space is available when the chickens need it. You can follow the link in my signature to get my ideas on what should go into the thought process when deciding how much space you need. It’s sort of written with coop in mind but the concepts are really based on total space available when needed.
Commercial operations do often use a total of around 2 square feet per chicken in a coop with no run, but they also normally trim their beak to prevent them from eating each other. Beak trimming is one management technique you can use to help shoehorn them together. But if you trim their beaks, you need to feed them mash instead of crumbles and pellets. It’s hard for them to pick up the individual bits of food. You are looking at a system in raising them. That’s a system most of us on this forum don’t use.
You don’t mention anything about your coop, management techniques, flock make-up, or climate so I have no idea how big your run should be in your unique situation.
You don’t say where you are or what your current weather is like, but most chicks are fully feathered out at five weeks. Weather is probably not an issue for you. I assume they are currently in the coop and are used to the coop as home? At five weeks you can just open the pop door and let them decide when they want to go into the run. Sometimes most of mine are in the run within 15 minutes but usually it takes a lot longer for them to get brave enough to go outside. I’ve had some go several days before the first one ventured out. Each flock is unique.
It’s kind of funny to watch them. The bold ones will peek out the pop door and be curious, but it takes a lot of courage for one to actually attempt it. After one goes out, the others usually follow but the interaction and flock dynamics are fun to watch, even at that age.
Their first few days they may stay out in the run instead of going into the coop at night. You need to check on then after dark and put them into the coop until they get used to doing that on their own. I’ve had some that did it by themselves from the start, but it is more normal that a few take a few lessons.
Good luck with it and welcome to the adventure.