The skin on the soles of my feet is so dry that it easily forms scratches that make it painful to walk, the weather here is very hot and dry so i tried applying vaseline but it was useless, is there any medicine that can moisturize my feet?

I recommend consulting a podiatrist to evaluate your feet and advise you. I assume the bottoms of your feet have abnormally thickened skin & many painful cracks or fissures. You're correct in blaming excessive dryness as part of the problem but if you have severe advanced problems with your soles, you'll need expert treatment and follow-up from a podiatrist. This may include special footwear&socks

Is the Vaseline a cream or jelly? Apply at night covering your feet. Pace your foot in a plastic bag and then place a sock over the bag covering your foot. This is called an occlusive dressing is best to bath feet prior to applying.