This is performed 1x through, kind of as a max effort, so weights should be where you can do 18 and not many more, since you’re only going through once. 

Modifications: 
Box Squat —-> Goblet Box Squat
Incline DB Curls —-> Use a swiss ball for the incline position
Tricep Cable Push Downs —> Use a Bandl
Ball Slams —-> Weighted Sit Ups