The answer to this question would be nine amino acid.
Essential amino acid is the amino acid that can't be produced by a human, so it needs to be fulfilled by their diet. There are 9 essential amino acid which was phenylalanine, methionine, leucine, valine, threonine, tryptophan, isoleucine, lysine, and histidine
But there are 6 conditionally essential amino acid that the synthesize might no be enough in some condition, so it will be needed in the diet too.
