Is there a link where I can download an older version of Airport Utility ?

If you have Catalina, you already have the latest version of AirPort Utility installed automatically on your Mac.

On your Mac......open Finder > Applications > Utilities > AirPort Utility

When AirPort Utility opens, click on the AirPort Utility menu in the upper left corner of your screen

Click About AirPort Utility

Note that you have Version 6.3.9 installed

That is the latest and most up to date version. Any other earlier version cannot be installed on your Mac because you already have the latest version on your Mac.

You can download an older version of AirPort Utility, but Apple won't allow it to run on your Mac unless you are using a very old operating system like Leopard, Snow Leopard and a very early version of Lion.......or.......until you try a few unsupported tricks that we do not recommend.

Click on the Apple icon in the upper left corner of your screen and then click on About This Mac. Post back with the version that appears there. Example......Catalina, Mojave, etc.

Is there something in particular that you need on the older version of AirPort Utility that current versions do not have?

Much easier if we know what version OSX you are on..

And generally .. since Lion I think Airport Utility is built in. Certainly Mountain Lion.