You have a 2003 or previous Atwood water heater. (probably a G6A-8E model)
The electric element is under a protective cover on rear bottom of water heater tank
Element has 120V AC directly via a 120V Circuit Breaker (turn it OFF)
Element has it's own set of t-stats on rear of tank and an ON/OFF switch back there (OEM)---RV Mfg added an additional in series ON/OFF switch (thank them cause the OEM at back of tank is a PITA)
Drain tank......get NEW NYLON plug (they come in 2 set)
NYLON has HIGH temp rating (400*F) and is softer then the aluminum so it's threads will be damaged vs the aluminum drain hole threads.
Element size is a 1 1/2" ----use a thin walled 6 point socket with extension.
Those 'element tools work IF you have ROOM and don't need to crank on it to loosen element.