Is it Possible to make...?

I've made many attempts but idk how I should form this script.

So I'm trying to make my script so that on q check if the targeted item during the key press is a valid item for equipping and then equip. I mainly want for this case to worry about "on q check if the targeted item during the key press is a valid item for equipping" and maybe have the code print"valid item" for now.

Mouse.KeyDown:connect(function(key)
    if (key == q) then
end)

many of my attempts were along the lines of this but i know there is probably a better way. Also in order for me to classify an item as a valid item i inserted a string value to the items called SBF so I used that thought to maybe implement FindFirstChild() stuff to identify then verify.