Suppose that instead of paying per hour, a moving company offers a flat rate of $1,200 for movers plus a truck for an eight hour day. If you hired this moving company and used them for the entire eight hours, how much consumer surplus would you gain?

the first part of the question is missing, so I looked for a similar one (see attached image):

the cost of hiring a moving crew for 8 hours = $250 per hour x 8 hours = $2,000

the competing company offered you a deal worth $1,200

since you expect to use the moving crew during the whole 8 hours, you will gain = $2,000 - $1,200 = $800 in consumer surplus

Consumer surplus is the difference between what a consumer (in this case you) are willing to pay for a good or service and the actual price of the good or service. Consumer should be willing to consumer a good or service as long as the consumer surplus is ≥ 0.