Active job

Concrete under floor

I have an old shed that I have been fixing up. When it rains hard the backyard floods and it gets under the flooring in the shed. I'd like to get some concrete under the flooring (floor is removed currently) to raise up the level so the water can't get into the shed. The area is 3m x 2.4m and would need concrete to be about 10cm deep. One of the photos shows what it looks like when it floods and before I replaced some joists and put gravel down. Thanks