Consider first the graph of the function |x|. It looks like this
for this graph, the vertex is located at (0,0). Now, the function |x-3| has the same graph as |x| but shifted 3 units to the right. It looks like this
In this case, the vertex is located at (3,0). Finally, for the function |x-3|-1 we shift the graph of |x-3| one unit down. So we get
This means that the vertex of this graph is (3,-1).