10m2 is insufficient here. Lack of rainfall in the summer months would turn it into a 'dustbowl'. What is quite clear to me is that the general (not organic) 'Free Range' figure here and in England of 4m2, means that the birds get exercise but no grass or insects. In fact to get a healthy amount of insects needs more like 1000m2 here. One local egg producer boasts that his get 9m2 free range, but that doesn't really achieve anything tangible.
So back to the original question. How much space do they need? There are welfare, sustainability and food issues here. If you were previously relying on an insect intake to supplement their feed with protein Azzdodd, you will now have to adjust accordingly. Laying hens need 15% and wheat gives them 8-10%. You may find they stop laying until you get the balance right. You may also find the yolks lose colour without a grass intake and you will need to find a substitute, unless your feed has chemical colourants in it already (yolk enhancers), as most pellets do.