Well those tiles appear to be 500mm squares and the base you lay needs to be larger than your shed in both dimensions. Your shed is 70" x 30" which is 1776mm x 762mm so the minimum multiple of 500mm to exceed that is 2000mm x 1000mm of base, which is 4 tiles x 2 tiles i.e., 2m².
Just to double check my working. 70 inches X 30 inches = ~1.35m² which means I need 22ft² / 2m² of this stuff right?
https://www.ebay.co.uk/itm/DRIVE-GRIDS-PLASTIC-PARKING-GRID-HEAVY-DUTY-MEMBRANE-ECO-BASE-GRAVEL-GRIDS-nw/192637420339?hash=item2cda15c333:m:mdMHZVGwP0tBBkU8vzKI--A&var=492779995444
Cheers.