Which one? There are a few from what I can gather, might help if you told us what DLC it was from. RailWorks\Assets\RSC\DonnerPass\RailVehicles\Diesel\F7 RailWorks\Assets\DTG\Clinchfield\RailVehicles\Diesel\F7 RailWorks\Assets\DTG\FeatherRiver\RailVehicles\Diesel\F7 RailWorks\Assets\Kuju\RailsimulatorUS\RailVehicles\Diesel\F7 And those are just the ones I have, and I hardly own any US content other than what I've bought as part of a bundle. I couldn't tell you which if any of these are Union Pacific though, I know nothing about US railways.
Wasatch Grade on the Steam store page lists Milepost Simulations as the developer, so look in the Assets folder for anything called Milepost Simulations or it may just be MS, or MPS, I don't know because I don't have that route. So it'll probably be something like RailWorks\Assets\*dev name*\Wasatch Grade\RailVehicles\Diesel\F7
Interesting, there you go OP that's the info you needed, As an aside I too have the JL folder but mine only has the WHL (West Highland Line South) in it, very different from all the US content you have BnR81.. Out of curiosity what does JL stand for, any idea?