Greetings @EMA03356!
While I do agree with @gulshankhurana on that, you might still want to have it that way for whatever reason. Should that be the case, here's how you would do it, but bear in mind that @gulshankhurana recommendation is far better than doint this, if you can do it as such.
Items property on Dropdown1
Distinct(LIST1;'CHOICE 1'.Value)
Items property on Dropdown2
Distinct(
Filter(
LIST1;
'CHOICE 1'.Value = Dropdown1.Selected.Value
);
'CHOICE 2'.Value
)
Items property on Dropdown3
Distinct(
Filter(
LIST1;
'CHOICE 1'.Value = Dropdown1.Selected.Value && 'CHOICE 2'.Value = Dropdown1_1.Selected.Value
);
'CHOICE 3'.Value
)
Hopefully this helped you out, otherwise, feel free to reply!