Any shed builder worth dealing with will be able to supply plans for council's DA process.
Those plans will specify the thickness of slab required for the floor loading AND for the footings, and it will specify the design of the footings & anchors to achieve the required rated strength.
1) Go to council and get their specs;
2) Go to your favoured shed supplier and give them the council specs and your requirements.
3) management of the building project depends on your talents - if you don't know what you're doing, talk to a local builder AND THEN to your supplier.
Good luck
