So, I purchased 2 1MN Afterburner’s and i went to my destination to pick them up, but why aren’t they in my inventory? I am so confused with this.
alt-r? Probably you bought in different station/system.
Open your assets window (click on this icon on the left toolbar):
Go to the search tab and search for 1MN afterburner, it will show you where the items are, right click the location, “set destination” and fly there.