Appwrite server error:

Before adding any item to the database I want to check whether the item with sam itemId and userId exists or not

Am I missing something?
What is the question you have? Quickly looking over it, it looks fine

When I click on add to cart button it return appwrite server error

Server error means something went wrong in the request, most likely the POST request. You added console.log, you should show them too.

I am getting to this error

This is my nextjs file

This is my appwrite file

I feel like you have slight understanding of JS, which is not a problem, but you are showing images which you cannot do much with. This is for getting the items, but not sending

I am getting error when I use Query or while creating that condition

Do you have attributes?

you mean in database

also what's after this?

No, in your database you have a collection, in the collection you have attributes

createDocument work perfectly