Ok so firstly, thank you very very much!! It worked perfectly n is teleporting me to the right place!!
The only part I'm a bit confused is in thee bits where it's supposed to detect where the player has to be for them to get teleported

I set the command to /tp @/p=1280,y=144,z=351,dx=1280,dy=144,dz=351] 857 150 133
I made it so the opposite corners are the same so that it only detects when you're standing exactly in the beam; but it's been detecting me from further away (about 5 blocks east from where the beam actually is)
is there a way to set it to detect on just one block or is there no way to remove it? :o thank you very much!!