The pineapple bobble pattern is based on 16 chains + 7 for your foundation chain. That means if you want 3 repeats of the pineapple bobble pattern you would multiply 16 X 3 = 48 + 7 = 55. So your based chain would be 55 chains long.
The pattern uses single crochet, chain, double crochet and the bobble stitch which is make 4 double crocht in same st leaving last loop of each double crochet on your hook (there should be five loops) yo and pull through all loops on hook.