Building carport

Yes, Simpson anchors would be fine. I work for a large kitset building manufacturer and this is one of the fixing options we use for our carports.

Make sure that the bolts are at least 100mm away (4 inch) from the edge of the concrete. Also you will need some braces running from the post diagonally up to the rafters - two per post. 700mm (30 inch long braces). Otherwise the carport will sway.

However there is no doubt that concreting the posts directly into the ground is the strongest fixing method. A 12 in x 12 in hole 48 inch deep would be sufficient

How thick is the concrete?
Will this be out in the open or attached to one side of the house?

Also look into a way to prevent moisture from working up the post from the concrete. Not sure what is the best way, I'm guessing some kind of small plastic around the bottom and sides of the post a few inches high may do. There may be a better way that I'm not aware of as well.

Just saying as I noticed my 3 support beams for my house are resting on a concrete footing but I can see a bit of rotting on the edges. Nothing major and the house is fairly old, but something I will need to look at eventually.

The concrete is 4", and it will be a free standing structure. We live in a wooded area which gives it some protection from strong winds.

The structure would need a perimeter foundation/footing system to install the weight of a carport on top. Minimally, the footings would be under the posts.
Do you know how the concrete pad was constructed?
Ron