First find the total number of basil leaves: 3 pots * 4 leaves/pot = <<3*4=12>>12 leaves
Then find the total number of rosemary leaves: 9 pots * 18 leaves/pot = <<9*18=162>>162 leaves
Then find the total number of thyme leaves: 6 pots * 30 leaves/pot = <<6*30=180>>180 leaves
Then add the number of each type of leaf to find the total number of leaves: 12 leaves + 162 leaves + 180 leaves = <<12+162+180=354>>354 leaves
#### 354