My best guess on the species is Canary winged parakeet, also called white wing parakeet or "Bee bee" parakeet. Scientific name is Brotogeris versicolurus. I'm not sure of the age but I would say closer to 3 months minimum, but it could be older.
Offer lots of soft fruits and vegetables, it might be dehydrated from being outside, and some millet to start. You can try regular parrot food later when it's eating by itself. I'm not sure what kind of food you have available in your country for parrots.
good job helping this little guy! Is that a parrot that can be found in the wild there? Can he fly? does he step up when you place your finger near his belly?
I'm trying to help you find out if this is a pet that someone is missing or if he is wild. Do you have access to bird seed?
I would (hypothetically) bet money that it is a juvenile of a smaller species in the Psittacula genus. Hard to judge what exact size the bird is by the pics, but since you said you live in Pakistan, that would makes sense for a Psittacula (genus that includes ringnecks, plumheaded, alexandrine, etc), also IME it looks exactly like a juvenile plumheaded (which can be found in Pakistan). Perhaps a wild one with no previous owner?
Not sure the species, but if you intend to keep him much longer I'd recommend a more appropriate cage... that one looks very rusty and that is very very bad for parrots. A larger size is a must if you intend to keep him, but short-term I'd look at getting a better carrier. Even a modified cat-carrier would be better.