Dispel Magic question

If I'm invisible with non detection but fail the counteract check vs True Seeing (assuming it's True Seeing), could I attempt to cast Dispel Magic on the True Seeing (even if my character isn't 100% sure it is True Seeing that is seeing him, just assuming it is since it's more likely to counteract my Nondetection then See Invisibility) or could my Dispel magic counteract some other effect on the creature?

As worded, there is no reason not to believe that you can cast dispel magic "on the spell effect that is letting me be seen"

If you've got a GM that insists you have to say exactly which spell, by name, you are trying to dispel or you can't try it, that's on your GM, not the rules.

But similarly you don't get to fling dispel magic at "whatever spell is on that guy" and have your GM pick one if there are more than one any more than you get to cast an attack spell without picking a target and have that still hit something.

Dispel magic makes no provisions for identifying a spell. Therefore, you can target any spell you're aware of, even if you don't know what it is.