I've been going from forum to forum to find some kind of diagram to find the filler plug. Already drained the trans fluid but now I can't find which is the filler plug. I see a couple of plugs but not sure which one it is.

 

It's a round headed plug on the right (passenger side) of the transmission. It's just above the pan and has a 8mm allen head. Make sure to search the forum for the proper filling method.

Or search the web for "Land Rover 6HP26x Transmission fluid level procedures" which will take you to another forum where the .pdf resides

 

Passenger side if LHD, just to clarify that a little.

This PDF will help you.

 

here is a copy of the procedure I was referring to...

 

Good tip when working on something that needs a fluid change (diffs, trans, etc) always locate and make sure you can remove the fill plug before you remove the drain plug.