You method declaration KeyValuePair<string, object>[] list states that it will accept an array so you need to convert your list to array like this

Test(myList.ToArray());

Given the original question, I think it's worth clarifying how the params keyword functions. It has to be a decorator on a 1D array, and simply allows an alternate syntax for calling the function.

For example if we have a string concatenation function:

public string Test(string[] names) {
    return String.Join(",", names);
}

This can be called using

Test(new[] { "Fred", "Wilma", "Pebbles"});

but the inclusion of the params keyword simply allows a friendlier looking calling syntax:

public string Test(params string[] names) {
    return String.Join(",", names);
}

Test("Fred", "Wilma", "Pebbles");

I'm not a huge fan of the params keyword, but I do sometimes use it to make calling code more readable (as in this example).

So when the OP asks "How can I do a conversion of the list to params?", the underlying truth is that you don't, as params is not a type and is simply a "syntactical sugar" feature to give an alternative syntax for passing in an array.

You should convert the list to form which is accepted as parameter. In this case convert List to Array

Hence,

var arrayParam = mylist.ToArray();
Test(arrayParam);