Command blocks

The command blocks in minecraft pe ( or atleast my minecraft ) are not working. When i want a Chain, unconditional, needs redstone command block, it lists at the bottom “ Impulse, unconditional, always active “ or “ Impulse, Conditional, needs redstone “ or “ Chain, unconditional, always active “ and finally “ Chain, conditional, needs redstone “. Please fix this cause out of all of the command blocks i have in one world, 2 of them actually work.

Thank you in advance

Stephen Junger