This is going to be the final product
make as many pillars as you want 3 tall out od any block, this is how many numbers to choose from for codes.
figure out your combination, for every number you use, put a block down on the ground and put redstone on top of it and one after. for everyone that isn't part of thr combination, put a block on the third block of the pillar and a redstone torch under it
put a sticky piaton after every redstone dust, and make a two long hole one deep in front of it.
at the secons block of the holes put redstone and connect them, then put a redstone torch on the far end bye the first pillar. if you have a lot of pillars (like me) you might want to add a repeater here.
at the end of each of the blocks on the top, connect them like in the picture, and two away from thr last pillar put 2 sticky pistons on top of eacher one behind all of the pillars. add redstone dust to the "bridge" on the top. make a 2x2 square behind the sticky pistons and behind the sticky pistons put a repeater, and on all the other blocks redstone dust.
add a lever to each of the original pillara and a sign above them insicating which number it is. and put the levers in the down position.
my code is 7-6-3 so i put those levers up and the door moved inwards, if you did all the steps corrsctly it should work!