Answer:
≅500,000 comparisons.
Step-by-step explanation:
The sequential search algorithm is, as its name express, a comparison method to search for a specific value in a list, sorted or not.
It starts with the first element in the list, compares the element with the searched value, if it is a match it stops, otherwise it moves to the next element and repeats.
In general, if the list size is X, the average number of comparisons is:

Solving for X=1,000,000, the result is ≅500,000 comparisons.