>> How Many Guineas Would It Take ,,,

[PeepsCA]

Adult Guineas need 4 sq ft of floor space in the coop per bird... so 2 would be comfy, 3 would be a little over cozy. Guineas like elbow room... and high perches.
IMO a 3'x3' coop isn't very Guinea friendly, but it may work out fine if you raise them in it from keets

 

[speckledhen]

You may get 3-4, 5 tops in that tiny coop if they only are in there for the night. Guineas are about 4 lb or so, smaller than a standard breed chicken, but larger than a bantam. Just read up all you can on guineas because they really are not one thing like a chicken in the way they act.

 

[Whittni]

Yup, that's just where I'd lock them up at night to be safe.

 

[speckledhen]

When I said 5, that was really pushing it for space, but I wouldn't advise that many if there was ever a time they'd need to be locked in due to bad weather or when you weren't home or whatever. Guineas usually like to roost as high as possible, but if they roost high, they also need lots of room to fly down so a small space like that wouldn't give them room. Anyway, hopefully, you can figure it out.

 

[Whittni]

Yeah, I'd already googled it...it needs to be as high as my fence, their coop