Question

But a scorpion is having eyes to see but then why it is using its legs to find its prey

Answer 1

Even with all those eyes, scorpions can't see very well! Yet the sensitivity of their eyes is among the highest in all arthropods and dependent on the kinds of habitats in which they live. In general terms, however, their eyes mostly tell movement and light from dark.
Once the prey is within reach, it is grabbed with the pincers and crushed. Most scorpions use their venomous sting only if needed, as it takes a lot of body energy to produce more venom. Younger and smaller scorpions may use their stinger more often than older and larger ones.