open the files for the game by right clicking on the game in your library and select "browse local files"
from here you'll see a very obvious folder named "save".
just drop the save into that folder and launch the game. you should be able to load the save. just make sure you launch the right version of the game (i.e. launch the paradise lost expansion to find the paradise lost save and vice versa)

when you load this you'll have catnip, crack-cola and 10 nukes. when i made this save i had killed every gary head already, so get high and get nuking, you should easily be able to kill mike j before he spawns any more gary heads

save: <google drive link>[drive.google.com]

open the files for the game by right clicking on the game in your library and select "browse local files"
open the folder named "Paradise Lost"
within that folder is all of the data for the expansion, including the folder for saves "PLSave"
drag the save into this folder and launch the paradise lost expansion, the save should be accessible in game now

in this save your inventory will have 3 or 4 catnips. you should only need to smoke one to run to the exit. i also have a ton of waters in my inventory which you can spam for 2hp each healing, but honestly with the catnip it should be easy enough to run to the end of the trainyard and end the game

save: <google drive link>[drive.google.com]