VBIUD bond fund in my 401(k) how can I see what the historical returns are of it?

VBIUD how can I see what the historical returns of this 401(k) fund are? I know it’s a bond fund and I don’t think it’s available to anything before 401(k) holders so I can’t really see what returns are. Is there a way to see that or should I just look for the most similar one that is publicly available?