Move billiard table slate within same property

The 5 x Slate for a Full Size Billiard Table (12ft x 6ft) is in a container on our front lawn, We need some very strong people to move it from the container to our garage at the back of our property about 20 metres. We will require a trolley (possibly a piano trolley) to assist with move. We will hire one if person does not own one. The job must be done between the 3rd to 8th April. Each slate is 2.7ft by 6ft and 2 inches thick and weighs approx 150kg,