how do you check/fill auto trans fluid

i didnt see a dipstick,but i did see a drain plug on the pan and what looks like a check/fill plug on the side. however it says in the manual that it takes 10 qt. to fill up and i dont think from the bottom of pan to that plug is 10 qt. i dont want to drain it and not be able to get it back in. any help would be great as i want to change the filter and fluid.

there aint a dipstick on the p38.
Range Rover Transmission Service Description this should help

On post '99MY Cars the dipstick and tube were removed. The transmission is filled through the large plug on the front of the gearbox (where the dipstick tube would have gone in). The level should be checked with the engine running, which means filling the gearbox til it overflows, then run the engine, holding on the foot brake move through all the gears then back to park. W

With the engine still running, top up the gearbox as required til it overflows again.

Job done, very messy but job done.

mines got a dipstick! usually in the drivers seat!