VBA Unique values from 2 columns based on condition

Hello All,

I have 2 columns - A and B and I want to extract unique values from column A and B . When Column B is not null then it should be considered otherwise column A.

Below is the code I use to copy from 1 column,

Data.Range("F2:F" & lastrow).SpecialCells(xlCellTypeVisible).Copy
Anchor.Cells(10, 1).PasteSpecial
Anchor.Columns(1).RemoveDuplicates Columns:=Array(1)

how do I modify this to my requirement. Please provide your suggestions. Have attached an excel as an example.

Thanks