So I know that Investigators can drop items (or forced to drop them if they fail a check for example).

My question is, does picking 2 items counts as One Action or Two?

As in, the same pace where my investigator is has 2 items; to pick them up I use 2 actions or only one?

Thanks in advance and sorry if this was already clarified somewhere else.

I believe the rules reference says that a single trade action allows you to pick up as many items as you want.

I believe the rules reference says that a single trade action allows you to pick up as many items as you want.

This is 100% correct. You may also pick up the items and give those to another investigator in your space during the same trade action