This coming from an American editor:
The example you provided is not a complete sentence, and so it makes it more difficult to know whether you should use "which" or "that" in it. If you post the complete sentence, it might help.
But to answer your question about when to use "which" or "that":
"That" is used with essential clauses (also known as a restrictive clauses). "Which" is used with non-essential clauses (known as non-restrictive clauses).
So what is the difference between an essential clause and a non-essential clause? An essential clause is essential to the meaning of the whole sentence, and if you take it out, the meaning of the sentence that remains is changed. A non-essential clause is extra information that can be taken out of the sentence without causing the meaning of the sentence to change. You would also use a comma before the non-essential clause (before the "which" in this case).
Here's an example. See if you can figure out the difference in meaning and why one clause is essential and the other clause is non-essential:
A. The cars that Frank sells are lemons.
B. The cars, which Frank sells, are lemons.
In the first example, maybe we're looking at a bunch of cars in a used-car lot, and we say, "the cars that Frank sells are lemons." That would mean, perhaps, that Frank sells some of the cars in the lot, and the ones he sells are lemons. The other cars, which he doesn't sell, may be fine. (There's one right there.) If you take out the essential clause "that Frank sells," then all you're left with is, "The cars are lemons." We've taken out information that is defining (the ones that Frank sells). That defining information is called restrictive information.
In the second example, it's clear that that Frank sells all the cars that we're talking about, because the comma and "which" tell us that the clause is merely adding extra information, not restrictive information. If we take out that clause ("which Frank sells"), the meaning of the sentence is not changed. Maybe we miss out on the extra information that Frank happens to sell the cars we're talking about, but the meaning is still clear: The cars are lemons.
Hope that helps and doesn't confuse.