1997 Mercury Sable that will turn the key and everything will turn on but it won't start

I have a 97 Mercury Sable that won't start. It started once yesterday with no problem as I needed to move it so I could move my Ranger but when my boyfriend tried to start it 3 hours later it won't turn over. When you put the key in everything lights up including the radio, the dash, and the headlights but when you turn the key nothing. There isn't even a clicking noise for the starter. They tried jumping it but when they hook up the jumper cables they are getting sparks so we think the battery has power. I bought the car used so I did not get a remote just the key so I am not sure if it has an anti-theft system or not. I don't recall seeing a light that says theft so I was thinking it does not have an anti-theft but everyone keeps saying it does. Others are saying it's a fuel issue but I am not sure and am hoping you can point me in the right direction please!