what Makes you think you have the wrong dip stick?
Are you checking your fluid level correctly? Engine running in neutral?
your fluid isn’t low based on your pic…you are aware how to read that dip stick? The 2 dots are hight and low “cold” marks, the cross hatch’s are
“Hot” fluid level marks.
Your ”leak” as you call it, is most likely one of 2 things, you “dip stick“seal is leaking “very common” after long periods of no use because the torque converter is unloading fluid, or your pan gasket is leaking “very common“ and needs to be cleaned up, the only place a transmission will leak from at the torque converter area is the pump seal or the torque converter shaft seal…neither of these are uncommon, but in my opinion, probably not the issue. Looking at the pic? i don’t see anything serious ,your “weep hole” on the Converter cover is where fluid would drip from, is the “leak” leaving fluid on the ground?
As far as fluids, you can use any Dexron III or “equivalent“….that information will be on the container