After a recent update I have lost a partion on my c drive of 1tb , how can I get it back.

[WPCentral Question]

When I bought my computer it had windows 8 on and I upgraded to 10 about 6 months ago. They had made a mistake and I only had 2tb of memory instead of 3tb. They helped me by email and I installed another 1tb as a partition. This has disapeared after the update the other day along with all my data. what can I do