congratulations on your new family! My husband also made me a coop out of pallets, and we also started with 4 pullets (which turned out to be 3 pullets and a cockrel!) And now we have babies and have had to convert the disused stable into a chicken coop as the pallet coop has been outgrown!
Welcome @Maria Belen Gil Ruiz. Ya'll are going to have so much fun! Go ahead and start making plans for a bigger coop as @elaineinspain pointed out....the flock keeps growing whether by incubation, buying chicks, hens sitting on eggs. Hard to stay with just the original count, lol. They call it "chicken math" here on BYC.....