how to add transparency to a hex code

if you grab a hex code from google chances are it's a 6 digit number example #000000 (cuz that's the one i have open in my search bar right now) hex codes are actually 8 numbers though the above is black red-00 blue-00 yellow-00 (not sure if i have the colors in the right position) there's a hidden element you can control at the end of that hex however that element is called alpha it's automatically set to be 100% opaque however you can control this element by expanding your hex to 8 digits the last 2 determine opacity now as you can probably guess i don't know the exact codes that determine how transparent a hex is however i do know the value for 50% transparancy which is likely what you're looking for maybe a little more opaque than that so feel free to play around with it but the value for 50% transparency is 80 so if i wanted to make the above element #000000 transparent i'd type it as #00000080