I'm no expert but I think there is only one version of this site.
In other words, there's no mobile version of it.
It's not optimized for phone use.
We get what we get.

To make it easier:

Don't Google moparts.com or .org and click on the result.
If you do, it's going to open in your default browser which could be garbage.

Download a separate free browser app like opera, dolphin, Firefox,etc.
The Dolphin has been working well here lately.

Using the Dolphin browser app, type in moparts.org or . Com ....log in manually in it, zoom out and presto there's the whole screen.
Just as you'd see it on computer.
Heres how it looks.
The text is small but this is how it goes when there is no optimized mobile version of the site.
You have to zoom out to see the whole thing, but that screen stays zoomed out until you change it.

The black areas are only part of the picture, they don't actually show up on the screen when I'm viewing the site itself.

Give it a try.