I don't think Godot has an Asset Store/Marketplace like Unity and Unreal do. I do believe it has a store of sorts for extensions (correct me if I'm wrong). A good place to find game artwork is opengameart.org and itch.io. If you need scripts, what I did when I used Godot is browse YouTube tutorials, most of them have a link to the code used in the description, though some like to hide it behind a paywall.

If you've gone through the Godot doc you've probably seen this already, but just in case, Godot does have an Asset Library  of user contributed assets (code and artwork) that is accessible via web browser and (more conveniently) within the Godot editor, so it is similar to the integrated Unity and Unreal asset stores, the big difference being that everything in the Godot library is distributed under an open source license.

https://docs.godotengine.org/en/stable/tutorials/assetlib/what_is_assetlib.html

Have you tried https://godotmarketplace.com/ ?

If you are new to development, then, I think assets are the least to worry about right now. If it's 3D you would like to tackle, perhaps you can use placeholder objects such as different sized cubes or cylinders to move around and to interact with. For more visual fidelity, there are so many free 3D assets out there. Collecting separate assets will provide a better look for your game but their art style may differ so you may end up doing your own or hiring help later in the project.

It's usually easier to find proper 2D assets. One great source was mentioned above. Also, since you didn't mention that it should be free, there is also https://www.gamedevmarket.net/