I bought a scanner so that I could put on Facebook some of my old picture that I have collected over the years?

The first two pictures that I put on were the normal size but now they are too small and my profile picture is smaller than everyone elses. I've looker everywhere for a place to make them bigger when I put them on my post put I can't see one. I know I can click on the picture and make it larger once I put it on my post but others won't want to go to that trouble. can anyone tell me why my pictures are much smaller than they should be...thank you