How to properly do a 301 redirect for SEO?

We are implementing a new website.  We will be switching web servers when we go live.
So, right now, I have the page example.com/example old 1.htm on the server #1, which I want to redirect to server #2 and the page of example.com/example NEW 1.aspx.

I have several hundred of these to setup, and am trying to figure out if I need to actually copy the original page from the old server and web to the new server and new web?  I did one that way and setup the redirect in IIS by selecting the file, choosing "HTTP Redirect" and inputting the new URL, and it worked like a charm but didnt' test perfectly on some online redirect testers.... However, I want to keep things simple in the file structure of the new website if possible and I don't want all my old web pages in there (even though they'd be redirected and innaccessible).

So, I setup a new record in the "Web.Config" file without physically moving the corresponding file from the old site to the new site and it was:
<location path="ABOUT US.htm">
        <system.webServer>
            <httpRedirect enabled="true" destination="/t-about.aspx" exactDestination="true" childOnly="true" httpResponseStatus="Permanent" />
        </system.webServer>
    </location>

This correctly redirected the file from the old one to the new one, but it won't register as a 301 redirect in any online redirect testers I try because my old website is a domain name right now and the new one is simply an IP Address for testing.

Does only using the Web.Config not register as an SEO friendly redirect because of the IP Address deal, did I do something wrong, or does the "About Us.htm" old file actually physically have to also be in the new site and be redirected?


Thanks for any help anyone provides!