How to make Random.new return multiple values?

I was making a random terrain generator but I decided to use Random.new instead of math.random because I want people to be able to generate a world via a seed, if I use math.random, the props (like trees, rocks etc...) will generate randomly and not referencing the seed. However as I did Random.new(SEED) on every random condition, it chooses 1 prop and puts it on every block. How would I fix this using Random.new or straight up knowing how to put a seed in math.random?