stop by (somewhere) on the way (to somewhere)

This means to quickly go to a place before continuing to your final destination.

You usually indicate the destination with "to":

on the way to the airport

But "there" and "here" are exceptions to the rule. They don't use "to":

Was there any traffic on the way here?

there

When you're talking about going to a place, you usually use the word "to":

I was on my way to work.

We're going to Dallas for Christmas.

The word "there" is different, though. You use it by itself:

I was on my way there.

We're going there for Christmas.

"Here" and "home" work the same way:

I moved here in the early '90s.

We're driving home.