We can do the math to calculate how much that you need.
There are 61 cubic inches in 1 liter. Your 33 long has a 48" x 13" footprint.
1" of substrate depth is 48" x 13" x 1" = 624 cubic inches, 624 cubic inches ÷ 61 cubic inches per liter = 10.2 liters, purchase (1 x 9L bag + 1 x 3L bag)
2" of substrate depth = 10.2 liters per inch of substrate depth x 2" of substrate = 20.4 liters, purchase (2 x 9L bags + 1 x 3L bag)
3" of substrate depth = 10.2 liters per inch of substrate depth x 3" of substrate = 30.6 liters, purchase (3 x 9L bags + 1 x 3L bag)
4" of substrate depth = 10.2 liters per inch of substrate depth x 4" of substrate = 40.8 liters, purchase (4 x 9L bags + 2 x 3L bags)
5" of substrate depth = 10.2 liters per inch of substrate depth x 5" of substrate = 51.0 liters, purchase (5 x 9L bags + 2 x 3L bags)
These calculations will get you in the ballpark. This is how I found out how much Amazonia that I needed for my 40 breeder. You can decide what substrate depth that you want to have. Then you have to decide if you want some Amazonia Powder or Amazonia Multi-Type to go with your regular Amazonia. Or, if you want all Amazonia Multi-Type. Some people have 1" to 2" in front and 3" to 5" in the back.
Does this help you?