All the animals have 4 legs.
His 3 dogs will need 3 * 4 = <<3*4=12>>12 shoes.
His 2 cats will need 2 * 4 = <<2*4=8>>8 shoes.
His ferret will need 1 * 4 = <<1*4=4>>4 shoes.
Olly will need 12 + 8 + 4 = <<12+8+4=24>>24 shoes.
#### 24