can you say me are correct placed on the board? The distance between elements is measured 4mm. We will use FR4 material for PCB(1.2mm 4 Layers).
I assume you're asking about the distance between the ADuM1402 and AD7400A (see the marked up figure I've attached). There's no requirement in terms of the isolation rating, but you might want to leave space to accomodate an increased creepage package in the future if that might be required. The RI designated package provides 8 mm creepage and is 2.5 mm longer than the standard wide body SOIC (RW package). You can see the package drawings in the ADuM440x data sheet.