TP entity to other armorstand You must specify which player you wish to perform this action on

The problem is with the @e[name="Prison Guard"] selector; you cannot use spaces in selectors, nor can you put quotation marks around strings in selectors.

I believe the error you are getting is caused by Minecraft understanding the command as having 3 arguments, which matches the /tp overload that can be used in chat but not in command blocks:

Command : /minecraft:tp
<x> : @e[name=Prison
<y> : Guard"]
<z> : @e[type=ArmorStand,name=LogPrisonGuard1]

Some potential solutions are to:

1. Select the guard based on something else (e.g: position, tags, team)
2. Give the guard a name without spaces (Warden, perhaps?)
3. Use their CustomName NBT to first give them a tag, then select them from that tag.

For the third option, you'll need to run a command like this to add the tag:

/scoreboard players tag @e add IsPrisonGuard {CustomName:"Prison Guard"}

Then select them using: @e[tag=IsPrisonGuard]. This works because you can have spaces within quotations for NBT data, just not for selectors.

Fixed with /entitydata @e[name=Warden] {Rotation:[180f,4f]} This data tag effects the yaw and pitch of the entity, changing the way they look. If you still need to move the entity, and you are getting this problem, have one command block that tp's them to the place, then use the above command.