This is for a health project, just need a little help because some sites say there is no confirmed lethal dose but there has been people who have died from overdoses of LSD.

I have to do a research project and I have to find a lethal dose
for my body. Drugs such has Tynenol, advil, pepto bismol,
and such.

How do you calculate that?
Also, how do you find the ld50 of the drugs?

Pleaseeee helppp.