so your codes, e.g. B03MVJDJY2.SECONDARY.jpg, which are the new file name are in column B

Right-click the tab of the worksheet containing those codes and choose View Code from the popup menu.
Put the code in the resulting window.

Path = "I:\GHTest\2021 New Products\secondary images\"
looks correct, but SECONDARYIMAGE3.JPG should also be in this folder.

For r = 1 To 10 'or however many there are
FileCopy Path & sourceimage, Path & Range("B" & r).Value
Next
Assuming your codes in column B start at row 1 to row 10, then Range("B" & r).Value should be the new file name contained in each cell, e.g. B03MVJDJY2.SECONDARY.jpg

Click in the code and press F8 to step through it. While stepping through, if you hover the mouse over bits such as Range("B" & r).Value, the tooltip should show the name of the code in that cell.