Putting it on an existing slab may be a challenge. Typically there are footers located to support the steel Columns. The concrete is an integral part of the Structure. Do Not buy directly from a company that will not erect it, they wont be there to make sure it is right, By From A dealer that with get the thing done. American Buildings, Butler, Lester are a few.
It might be just as easy to cut holes in the slab for supports and put up a pole Barn. They have a wood frame, and steel sheeting. Much Cheaper than an all steel building.
__________________
|