In the case of a turkey burger (and most meat that is already lean), all that's changing is mass decreasing by roughly 50% due to water loss.
So, cooked turkey burgers (or chicken breast, for example) are roughly "twice as much" as the same mass of raw. Just make sure you measure it either raw or cooked, and use the appropriate nutritional data. Often on packages, if it comes raw, they will be indicating the raw figures, and vice versa (cooked = cooked calories) unless otherwise indicated.
In your case, you know the raw data, so just use that. What it weighs after cooking is irrelevant, unless you are using nutritional information that assumes it is cooked (which you clearly are not). Basically, what LV said. Everything is the same, don't worry about it.
