You're probably not going to be performing seated rows if you don't have a cable row machine. You could improvise with a resistance band but it won't simulate the right weight. The goal is to find a good cable row substitute that builds the same muscles and movements. Other rowing movements are a good choice - whether that's a bodyweight row or free weights. You can row with almost any of the equipment you'd find in a standard gym: a cable machine, t-bar, or just a dumbbell row.