The required cable stop on the derailleur itself is a bolt on item. It has a little plate that secured it under the existing cable clamp, and a swiveling housing stop.

Some of those Trek frames have the cable anchor on the bottom of the BB, some are more obviously on the back of the BB shell where you can see it.

https://www.ebay.com/itm/28476907449...gAAOSwN~diWke4